Lab Testing

29 Nov Lab Testing

Posted at 20:15h in Clinical Services, Testing by Sound Shape

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The Hypertension Institute of Nashville offers the following lab testing services:

Blood Glucose

Blood Glucose Testing

A blood glucose test measures the amount of a type of sugar, called glucose, in your blood. Glucose comes from carbohydrate foods. It is the main source of energy used by the body. Insulin is a hormone that helps your body’s cells use the glucose. Insulin is produced in the pancreas and released into the blood when the amount of glucose in the blood rises.

Normally, your blood glucose levels increase slightly after you eat. This increase causes your pancreas to release insulin so that your blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels.

Several different types of blood glucose tests are used.

Fasting blood sugar (FBS) measures blood glucose after you have not eaten for at least 8 hours. It is often the first test done to check for prediabetes and diabetes.
2-hour postprandial blood sugar measures blood glucose exactly 2 hours after you start eating a meal.
Random blood sugar (RBS) measures blood glucose regardless of when you last ate. Several random measurements may be taken throughout the day. Random testing is useful because glucose levels in healthy people do not vary widely throughout the day. Blood glucose levels that vary widely may mean a problem. This test is also called a casual blood glucose test.
Oral glucose tolerance test is used to diagnose prediabetes and diabetes. An oral glucose tolerance test is a series of blood glucose measurements taken after you drink a sweet liquid that contains glucose. This test is commonly used to diagnose diabetes that occurs during pregnancy (gestational diabetes). This test is not commonly used to diagnose diabetes in a person who is not pregnant.

Why It Is Done

Blood glucose tests are done to:

Check for diabetes.
Monitor treatment of diabetes.
Check for diabetes that occurs during pregnancy (gestational diabetes).

Determine if an abnormally low blood sugar level (hypoglycemia) is present. A test to measure blood levels of insulin and a protein called C-peptide may be done along with a blood glucose test to determine the cause of hypoglycemia.

Results

Normal

A blood glucose test measures the amount of a type of sugar, called glucose, in your blood.
Results are often ready in 1 to 2 hours. Glucose levels in a blood sample taken from your vein (called a blood plasma value) may differ a little than glucose levels checked with a finger stick.

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, Dr. Houston will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Blood Glucose
Fasting blood glucose:	70-99 (3.9-5.5 mmol/L)
2 hours after eating (postprandial):	70-145 mg/dL (3.9-8.1 mmol/L)
Random (casual):	70-125 mg/dL (3.9-6.9 mmol/L)

Many conditions can change your blood glucose levels. Dr. Houston will discuss any significant abnormal results with you in relation to your symptoms and past health.

High values

You may have diabetes. But Dr. Houston will not use just one test result to diagnose you with the condition.

The American Diabetes Association (ADA) criteria for diagnosing diabetes are met when any of the following results have been repeated on at least two different days:
- A fasting blood glucose level is 126 mg/dL (7.0 mmol/L) or higher.
- A 2-hour oral glucose tolerance test result is 200 mg/dL (11.1 mmol/L) or higher
- Symptoms of diabetes are present and a random blood glucose test is 200 mg/dL (11.1 mmol/L) or higher. Symptoms of diabetes include increased thirst and frequent urination(especially at night), unexplained increase in appetite, unexplained weight loss, fatigue, erection problems, blurred vision, and tingling or numbness in the hands or feet.
If your fasting blood glucose level measures in the range of 100 mg/dL (5.6 mmol/L) to 125 mg/dL (6.9 mmol/L), you are considered to have prediabetes (impaired fasting glucose), and you have an increased chance of getting diabetes.
Other conditions that can cause high blood glucose levels include severe stress, heart attack, stroke,Cushing’s syndrome, medicines such as corticosteroids, or excess production of growth hormone (acromegaly).

Low values

A fasting glucose level below 40 mg/dL (2.2 mmol/L) in women or below 50 mg/dL (2.8 mmol/L) in men that is accompanied by symptoms of hypoglycemia may mean you have an insulinoma, a tumor that produces abnormally high amounts of insulin.
Low glucose levels also may be caused by:

Addison’s disease.
Decreased thyroid hormone levels (hypothyroidism).
A tumor in the pituitary gland.
Liver disease, such as cirrhosis.
Kidney failure.
Malnutrition or an eating disorder, such as anorexia.
Medicines used to treat diabetes.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Eating or drinking less than 8 hours before a fasting blood test or less than 2 hours before a 2-hour postprandial test.
Drinking alcohol.
Illness or emotional stress, smoking, and caffeine.

Taking a medicine, such as birth control pills, medicines used to treat high blood pressure, phenytoin (Dilantin), furosemide (Lasix), triamterene (Dyrenium, Dyazide), hydrochlorothiazide (Esidrix, Oretic), niacin, propranolol (Inderal), or corticosteroids (prednisone), can cause changes in your test results. Make sure Dr. Houston knows about any medicines you take and how often you take them.

Blood Urea Nitrogen (BUN)

Blood Urea Nitrogen

A blood urea nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea. Urea is made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine.
A BUN test is done to see how well your kidneys are working. If your kidneys are not able to remove urea from the blood normally, your BUN level rises. Heart failure, dehydration, or a diet high in protein can also make your BUN level higher. Liver disease or damage can lower your BUN level. A low BUN level can occur normally in the second or third trimester of pregnancy.

Blood urea nitrogen to creatinine ratio (BUN:creatinine)

A BUN test may be done with a blood creatinine test. The level of creatinine in your blood also tells how well your kidneys are working-a high creatinine level may mean your kidneys are not working properly. Blood urea nitrogen (BUN) and creatinine tests can be used together to find the BUN-to-creatinine ratio (BUN:creatinine). A BUN-to-creatinine ratio can help Dr. Houston check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.

Why It Is Done

A blood urea nitrogen (BUN) test is done to:

See if your kidneys are working normally.
See if your kidney disease is getting worse.
See if treatment of your kidney disease is working.
Check for severe dehydration. Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to go up.

Results

A blood urea nitrogen (BUN) test measures the amount of nitrogen in your blood that comes from the waste product urea.

Normal

Blood urea nitrogen (BUN)
Normal:	6-20 milligrams per deciliter (mg/dL) or 2.1-7.1 millimoles per liter (mmol/L)
BUN-to-creatinine ratio
Normal:	10:1 to 20:1

High values

A high BUN value can mean kidney injury or disease is present. Kidney damage can be caused bydiabetes or high blood pressure that directly affect the kidneys. High BUN levels can also be caused by blockage of the urinary tract (by a kidney stone or tumor) or low blood flow to the kidneys caused bydehydration or heart failure.
Many medicines may cause a high BUN. Be sure to tell Dr, Houston about all the nonprescription and prescription medicines you take.
A high BUN value may be caused by a high-protein diet, Addison’s disease, tissue damage (such as from severe burns), or from bleeding in the gastrointestinal tract.
High BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be caused by shockor severe dehydration. A blockage in the urinary tract (such as a kidney stone) can cause a high BUN-to-creatinine ratio. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tractor respiratory tract.

Low values

A low BUN value may be caused by a diet very low in protein, malnutrition, or severe liver damage.
Drinking excessive amounts of liquid may cause overhydration and cause a low BUN value.
Women and children may have lower BUN levels than men because of how their bodies break down protein.
A low BUN-to-creatinine ratio may be caused by a diet low in protein, a severe muscle injury calledrhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH sometimes occurs with lung disease, cancer, diseases of the central nervous system, and the use of certain medicines.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking medicines, such as amphotericin B (such as Fungizone), nafcillin, aminoglycosides, kanamycin (Kantrex), tobramycin (Nebcin), corticosteroids, tetracycline antibiotics, and, rarely, the antibiotic chloramphenicol (Chloromycetin).
Taking diuretics, which can cause dehydration.
Your age. BUN levels rise as you get older.
Your sex. Women and children have lower BUN levels than men.

C-Reactive Protein (CRP)

A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood. C-reactive protein measures general levels of inflammation in your body.

High levels of CRP are caused by infections and many long-term diseases. But a CRP test cannot show where the inflammation is located or what is causing it. Other tests are needed to find the cause and location of the inflammation.

Why It Is Done

A C-reactive protein (CRP) test is done to:

Check for infection after surgery. CRP levels normally rise within 2 to 6 hours of surgery and then go down by the third day after surgery. If CRP levels stay elevated 3 days after surgery, an infection may be present.
Identify and keep track of infections and diseases that cause inflammation, such as:
- Cancer of the lymph nodes (lymphoma).
- Diseases of the immune system, such as lupus.
- Painful swelling of the blood vessels in the head and neck (giant cell arteritis).
- Painful swelling of the tissues that line the joints (rheumatoid arthritis).
- Swelling and bleeding of the intestines (inflammatory bowel disease).
- Infection of a bone (osteomyelitis).
Check to see how well treatment is working, such as treatment for cancer or for an infection. CRP levels go up quickly and then become normal quickly if you are responding to treatment measures.

A special type of CRP test, the high-sensitivity CRP test (hs-CRP), may be done to find out if you have an increased chance of having a sudden heart problem, such as a heart attack. Inflammation can damage the inner lining of the arteries and make having a heart attack more likely. But the connection between high

Results

A C-reactive protein (CRP) test is a blood test that measures the amount of a protein called C-reactive protein in your blood.

Normal

Results are usually available within 24 hours.

C-reactive protein (CRP)
Normal:	0-1.0 mg/dL or less than 10 mg/L (SI units)

Any condition that results in sudden or severe inflammation may increase your CRP levels.
Some medicines may decrease your CRP levels.

High-sensitivity C-reactive protein (hs-CRP) levels

The hs-CRP test measures your risk for heart problems. It may be done to find out if you have an increased chance of having a sudden heart problem, such as a heart attack. But the connection between high CRP levels and heart attack risk is not very well-understood.

High-sensitivity C-reactive protein (hs-CRP) levels
Less than 1.0 mg/L	Lowest risk
1.0 to 3.0 mg/L	Average risk
More than 3.0 mg/L	Highest risk

Many conditions can change CRP levels. Dr. Houston will talk with you about any abnormal results that may be related to your symptoms and past health.

What Affects the Test

The test results may not be helpful if:

You have just exercised.
You have an infection.
You have an intrauterine device (IUD) in place.
You are pregnant.
You are very overweight (obese).

Calcium (Ca) in Blood

A test for calcium in the blood checks the calcium level in the body that is not stored in the bones. Calcium is the most common mineral in the body and one of the most important. The body needs it to build and fix bones and teeth, help nerves work, make muscles squeeze together, help blood clot, and help the heart to work. Almost all of the calcium in the body is stored in bone. The rest is found in the blood.

Normally the level of calcium in the blood is carefully controlled. When blood calcium levels get low (hypocalcemia), the bones release calcium to bring it back to a good blood level. When blood calcium levels get high (hypercalcemia), the extra calcium is stored in the bones or passed out of the body in urine and stool. The amount of calcium in the body depends on the amount of:

Calcium you get in your food.
Calcium and vitamin D your intestines absorb.
Phosphate in the body.
Certain hormones, including parathyroid hormone, calcitonin, and estrogen in the body.

Vitamin D and these hormones help control the amount of calcium in the body. They also control the amount of calcium you absorb from food and the amount passed from the body in urine. The blood levels of phosphate are closely linked to calcium levels and they work in opposite ways: As blood calcium levels get high, phosphate levels get low, and the opposite is also true.

It is important to get the right amount of calcium in your food because the body loses calcium every day. Foods rich in calcium include dairy products (milk, cheese), eggs, fish, green vegetables, and fruit. Most people who have low or high levels of calcium do not have any symptoms. Calcium levels need to be very high or low to cause symptoms.

Why It Is Done

A blood calcium test may be done:

To check for problems with the parathyroid glands or kidneys, certain types of cancers and bone problems, or inflammation of the pancreas (pancreatitis).
To find a reason for an abnormal electrocardiogram (EKG) test.
After a kidney transplant.
To see if your symptoms may be caused by a very low calcium level in the blood. Such symptoms may include muscle cramps, spasms, and twitching and tingling in the fingers and around the mouth.
To see if your symptoms may be caused by a very high calcium level in the blood. Such symptoms may include weakness, lack of energy, not wanting to eat, nausea and vomiting, constipation, urinating a lot, belly pain, or bone pain.
As part of a routine blood test.

A blood calcium test cannot be used to check for a lack of calcium in your diet or for the loss of calcium from the bones (osteoporosis). The body can have normal calcium levels even if your diet does not have enough calcium in it. Other tests, such as bone mineral density, check the amount of calcium in the bones.

Results

A test for calcium in the blood checks the calcium level in the body that is not stored in the bones.

Normal

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Calcium in blood
Adults:	8.8-10.4 milligrams per deciliter (mg/dL) or 2.2-2.6 millimoles per liter (mmol/L)

An ionized calcium test checks the amount of calcium that is not attached to protein in the blood. The level of ionized calcium in the blood is not affected by the amount of protein in the blood.

Ionized calcium
Adults:	4.65-5.28 mg/dL or 1.16-1.32 mmol/L

High values

High values of calcium may be caused by:

Hyperparathyroidism.
Cancer, including cancer that has spread to the bones.
Tuberculosis.
Being on bed rest for a long time after a broken bone.
Paget’s disease.

Low values

Low values of calcium may be caused by:

A low level of the blood protein albumin (hypoalbuminemia).
Hypoparathyroidism.
High levels of phosphate in the blood, which can be caused by kidney failure, laxative use, and other things.
Malnutrition caused by diseases such as celiac disease, pancreatitis, and alcoholism.
Osteomalacia.
Rickets.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking calcium or vitamin D in any form including milk, antacids, or supplements right before the test.
Taking medicines, such as diuretics. Many medicines can affect calcium levels in the blood.
Having dialysis.
Having a high volume blood transfusion or many blood transfusions in a short period of time.

Catecholamines in Blood

A test for catecholamines measures the amount of the hormones epinephrine, norepinephrine, and dopamine in the blood. These catecholamines are made by nerve tissue, the brain, and the adrenal glands. Catecholamines help the body respond to stress or fright and prepare the body for “fight-or-flight” reactions.

The adrenal glands make large amounts of catecholamines as a reaction to stress. The main catecholamines are epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine. They break down into vanillylmandelic acid (VMA) and metanephrine. Metanephrine is often measured during a catecholamine test.

Catecholamines increase heart rate, blood pressure, breathing rate, muscle strength, and mental alertness. They also lower the amount of blood going to the skin and increase blood going to the major organs, such as the brain, heart, and kidneys.

Certain rare tumors (such as a pheochromocytoma) can increase the amount of catecholamines in the blood. This causes high blood pressure, excessive sweating, headaches, fast heartbeats (palpitations), and tremors.

Why It Is Done

A catecholamine test is done to help diagnose a tumor in the adrenal glands called a pheochromocytoma. Catecholamine levels in the blood can change quickly, so it may be hard to find high values in a single blood sample. But a special compound, metanephrine, may be found in the blood, which may mean a pheochromocytoma is present. Doctors may want to do a urine test that shows catecholamine levels over 24 hours.

Results

A test for catecholamines measures the amount of epinephrine, norepinephrine, and dopamine in the blood. These catecholamines are made by nerve tissue, the brain, and the adrenal glands.

Normal

Chloride (Cl)

A chloride test measures the level of chloride in your blood or urine. Chloride is one of the most importantelectrolytes in the blood. It helps keep the amount of fluid inside and outside of your cells in balance. It also helps maintain proper blood volume, blood pressure, and pH of your body fluids. Tests for sodium, potassium, and bicarbonate are usually done at the same time as a blood test for chloride.

Most of the chloride in your body comes from the salt (sodium chloride) you eat. Chloride is absorbed by your intestines when you digest food. Extra chloride leaves your body in your urine.

Sometimes a test for chloride can be done on a sample of all your urine collected over a 24-hour period (called a 24-hour urine sample) to find out how much chloride is leaving your body in your urine.

Chloride can also be measured in skin sweat to test for cystic fibrosis.

Why It Is Done

A test for chloride may be done to:

Check your chloride level if you are having symptoms such as muscle twitching or spasms, breathing problems, weakness, or confusion.
Find out whether you have kidney or adrenal gland problems.
Help find the cause for high blood pH. A condition called metabolic alkalosis can be caused by a loss of acid from your body (for example, from a loss of electrolytes through prolonged vomiting or diarrhea). You may also have metabolic alkalosis if your body loses too much sodium or you eat too much baking soda (sodium bicarbonate).

Results

A chloride test measures the level of chloride in your blood or urine. Chloride is one of the most importantelectrolytes in the blood, along with sodium, potassium, and calcium. Chloride helps keep the amount of fluid inside and outside of your cells in balance.

Normal

Chloride in Blood
Adult:	96-106 milliequivalents per liter (mEq/L) or 96-106 millimoles per liter (mmol/L)
Child:	90-110 mEq/L or 90-110 mmol/L
Newborn:	96-113 mEq/L or 96-113 mmol/L

Chloride in Urine
Adult:	140-250 mEq per 24 hours or 140-250 mmol per day
Child (10-14 years):	64-176 mEq/24 hours or 64-176 mmol/day
Child (younger than 6 years):	15-40 mEq/24 hours or 15-40 mmol/day

Abnormal

High chloride levels may be caused by:

Dehydration, such as from diarrhea or vomiting.
Eating a lot of salt.
Kidney disease.
An overactive parathyroid gland (hyperparathyroidism).

Low chloride levels may be caused by:

Conditions that cause too much water to build up in the body, such as with syndrome of inappropriate antidiuretic hormone secretion (SIADH).
Addison’s disease.
A condition that raises the pH of the blood above the normal range (metabolic alkalosis).
Heart failure.
Ongoing vomiting.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

The amount of water in your body. If you are dehydrated, your chloride level is increased and if you are overhydrated, your chloride level is decreased.
Some medicines, such as corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), estrogens, male hormones (androgens), some blood pressure medicines, cholestyramine (such as Questran), and some “water pills” (diuretics).
Failing to collect exactly 24 hours of urine during a 24-hour urine test for chloride.

Cholesterol and Triglycerides Tests

Cholesterol and triglyceride tests are blood tests that measure the total amount of fatty substances (cholesterol and triglycerides) in the blood.

Cholesterol travels through the blood attached to a protein. This cholesterol-protein package is called a lipoprotein. Lipoprotein analysis (lipoprotein profile or lipid profile) measures blood levels of total cholesterol,LDL cholesterol, HDL cholesterol, and triglycerides.

Cholesterol. The body uses cholesterol to help build cells and produce hormones. Too much cholesterol in the blood can build up inside arteries, forming what is known as plaque. Large amounts of plaque increase your chances of having a heart attack or stroke.
HDL (high-density lipoprotein) helps remove fat from the body by binding with it in the bloodstream and carrying it back to the liver for disposal. It is sometimes called “good” cholesterol. A high level of HDL cholesterol may lower your chances of developing heart disease or stroke.
LDL (low-density lipoprotein) carries mostly fat and only a small amount of protein from the liver to other parts of the body. It is sometimes called “bad cholesterol.” A high LDL cholesterol level may increase your chances of developing heart disease.
VLDL: (very low-density lipoprotein) contains very little protein. The main purpose of VLDL is to distribute the triglyceride produced by your liver. A high VLDL cholesterol level can cause the buildup of cholesterol in your arteries and increases your risk of heart disease and stroke.
Triglycerides are a type of fat the body uses to store energy and give energy to muscles. Only small amounts are found in the blood. Having a high triglyceride level along with a high LDL cholesterol may increase your chances of having heart disease more than having only a high LDL cholesterol level.

Some medical experts recommend routine cholesterol and triglyceride testing to screen for problems that affect the way cholesterol is produced, used, carried in the blood, or disposed of by the body. Others may choose to routinely measure only total cholesterol and HDL levels.

Why It Is Done

Cholesterol and triglyceride testing is done:

As part of a routine physical exam to screen for a lipid disorder.
To check your response to medicines used to treat lipid disorders.
To help determine your chances of having of heart disease, especially if you have other risk factors for heart disease or symptoms that suggest heart disease is present.
If you have unusual symptoms, such as yellow fatty deposits in the skin (xanthomas), which may be caused by a rare genetic disease that causes very high cholesterol levels.

Results

Cholesterol and triglyceride tests are blood tests that measure the total amount of fatty substances (cholesterol and triglycerides) in the blood. Results are usually available within 24 hours.

Cholesterol and triglyceride levels vary according to your age and sex. The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, Dr. Houston will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Cholesterol and triglycerides*
Total cholesterol	Desirable:	Less than 200milligrams per deciliter (mg/dL) Less than 5.2millimoles per liter (mmol/L)
	Borderline high:	200-239 mg/dL 5.2-6.2 mmol/L
	High:	240 mg/dL or higher 6.2 mmol/L or higher
HDL cholesterol	High (desirable):	60 mg/dL or higher 1.6 mmol/L or higher
	Acceptable:	40-60 mg/dL 1.0-1.6 mmol/L
	Low (undesirable):	Less than 40 mg/dL Less than 1.0 mmol/L
LDL cholesterol	Optimal:	Less than 100 mg/dL (less than 70 mg/dL for people at high risk for a heart attack) Less than 2.6 mmol/L (less than 1.8 mmol/L for people at high risk for a heart attack)
	Near optimal:	100-129 mg/dL 2.6-3.3 mmol/L
	Borderline high:	130-159 mg/dL 3.4-4.1 mmol/L
	High:	160-189 mg/dL 4.1-4.9 mmol/L or higher
	Very high:	190 mg/dL or higher 4.9 mmol/L or higher
VLDL cholesterol	Optimal:	30 mg/dL or less 0.78 mmol/L or less
Triglycerides	Normal:	Less than 150 mg/dL Less than 1.7 mmol/L
	Borderline high:	150-199 mg/dL 1.7-2.3 mmol/L
	High:	200-499 mg/dL 2.3-5.6 mmol/L
	Very high:	500 mg/dL or higher 5.6 mmol/L or higher
*The figures in this table are provided by the National Cholesterol Education Program (NCEP) of the National Institutes of Health (NIH).

An HDL level of 60 mg/dL (1.5 mmol/L) or higher protects against heart disease.
An HDL cholesterol level less than 40 mg/dL (1.0 mmol/L) raise your risk of developing heart disease, especially if you also have high total cholesterol levels.
The ratio of total cholesterol to “good” (HDL) cholesterol may be important, especially if total cholesterol is high.
Very high cholesterol and triglyceride levels may be caused by an inherited form of high cholesterol (hypercholesterolemia or hyperlipidemia).
Talk with your doctor about other things that raise your risk for heart problems. Your doctor may change your goals for cholesterol levels if you have other risk factors for coronary artery disease, such as:
- Smoking.
- High blood pressure.
- Diabetes.
- Low HDL cholesterol (less than 40 mg/dL).
- Family history of early CAD.
- You are a man and older than 45, or you are a woman and older than 55.
If you have a very high risk of having a heart attack, Dr. Houston may want your LDL level to be less than 70 mg/dL. You may be at high risk if you smoke and have coronary artery disease, or if you have coronary artery disease and diabetes, acute coronary syndrome, or metabolic syndrome.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Medicines, such as diuretics, corticosteroids, male sex hormones (androgens), tranquilizers, estrogen,birth control pills, antibiotics, and niacin (vitamin B3).
Physical stress, such as infection, heart attack, surgery.
Eating 9 to 12 hours before the test.
Other conditions, such as hypothyroidism, diabetes, or kidney or liver disease.
Alcohol or drug abuse or withdrawal.
Liver disease (such as cirrhosis or hepatitis), malnutrition, or hyperthyroidism.
Pregnancy. Values are the highest during the third trimester and usually return to the prepregnancy levels after delivery of the baby.

Complete Blood Count (CBC)

A complete blood count (CBC) gives important information about the kinds and numbers of cells in the blood, especially red blood cells , white blood cells , and platelets. A CBC helps Dr. Houston check any symptoms, such as weakness, fatigue, or bruising, you may have. A CBC also helps him or her diagnose conditions, such as anemia, infection, and many other disorders.

A CBC test usually includes:

White blood cell (WBC, leukocyte) count. White blood cells protect the body against infection. If an infection develops, white blood cells attack and destroy the bacteria, virus, or other organism causing it. White blood cells are bigger than red blood cells but fewer in number. When a person has a bacterial infection, the number of white cells rises very quickly. The number of white blood cells is sometimes used to find an infection or to see how the body is dealing with cancer treatment.
White blood cell types (WBC differential). The major types of white blood cells are neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Immature neutrophils, called band neutrophils, are also part of this test. Each type of cell plays a different role in protecting the body. The numbers of each one of these types of white blood cells give important information about the immune system. Too many or too few of the different types of white blood cells can help find an infection, an allergic or toxic reaction to medicines or chemicals, and many conditions, such as leukemia.
Red blood cell (RBC) count. Red blood cells carry oxygen from the lungs to the rest of the body. They also carry carbon dioxide back to the lungs so it can be exhaled. If the RBC count is low (anemia), the body may not be getting the oxygen it needs. If the count is too high (a condition called polycythemia), there is a chance that the red blood cells will clump together and block tiny blood vessels (capillaries). This also makes it hard for your red blood cells to carry oxygen.
Hematocrit (HCT, packed cell volume, PCV). This test measures the amount of space (volume) red blood cells take up in the blood. The value is given as a percentage of red blood cells in a volume of blood. For example, a hematocrit of 38 means that 38% of the blood’s volume is made of red blood cells. Hematocrit and hemoglobin values are the two major tests that show if anemia or polycythemia is present.
Hemoglobin (Hgb). The hemoglobin molecule fills up the red blood cells. It carries oxygen and gives the blood cell its red color. The hemoglobin test measures the amount of hemoglobin in blood and is a good measure of the blood’s ability to carry oxygen throughout the body.
Red blood cell indices. There are three red blood cell indices: mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). They are measured by a machine and their values come from other measurements in a CBC. The MCV shows the size of the red blood cells. The MCH value is the amount of hemoglobin in an average red blood cell. The MCHC measures the concentration of hemoglobin in an average red blood cell. These numbers help in the diagnosis of different types of anemia. Red cell distribution width (RDW) can also be measured which shows if the cells are all the same or different sizes or shapes.
Platelet (thrombocyte) count. Platelets (thrombocytes) are the smallest type of blood cell. They are important in blood clotting. When bleeding occurs, the platelets swell, clump together, and form a sticky plug that helps stop the bleeding. If there are too few platelets, uncontrolled bleeding may be a problem. If there are too many platelets, there is a chance of a blood clot forming in a blood vessel. Also, platelets may be involved in hardening of the arteries (atherosclerosis).
Mean platelet volume (MPV). Mean platelet volume measures the average amount (volume) of platelets. Mean platelet volume is used along with platelet count to diagnose some diseases. If the platelet count is normal, the mean platelet volume can still be too high or too low.

Dr. Houston may order a blood smear test to be done at the same time as a CBC but it is not part of the regular CBC test. In this test, a drop of blood is spread (smeared) on a slide and stained with a special dye. The slide is looked at under a microscope. The number, size, and shape of red blood cells, white blood cells, and platelets are recorded. Blood cells with different shapes or sizes can help diagnose many blood diseases, such as leukemia, malaria, or sickle cell disease.

Results

Normal

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Normal values for the complete blood count (CBC) tests depend on age, sex, how high above sea level you live, and the type of blood sample.Dr. Houston may use all the CBC values to check for a condition. For example, the red blood cell (RBC) count, hemoglobin (Hgb), and hematocrit (HCT) are the most important values needed to tell whether a person has anemia, but the red blood cell indices and the blood smear also help with the diagnosis and may show a possible cause for the anemia.

To see if the white blood cell (WBC, leukocyte) count is good and how the cells look on the smear, Dr. Houston will look at both the number (WBC count) and the WBC differential. To see whether there are too many or too few of a certain type of cell, your doctor will look at the total count and the percentage of that particular cell. There are normal values for the total number of each type of white cell.

Pregnancy can change these blood values. Your doctor will talk with you about normal values during eachtrimester of your pregnancy.

White blood cell (WBC, leukocyte) count
Men and nonpregnant women:	5,000-10,000 WBCs per cubic millimeter (mm3) or 5.0-10.0 x 109 WBCs per liter (L)

White blood cell types (WBC differential)
Neutrophils:	50%
Band neutrophils:	3%-6%
Lymphocytes:	25%-40%
Monocytes:	3%-7%
Eosinophils:	0%-3%
Basophils:	0%-1%

Red blood cell (RBC) count
Men:	4.5-5.5 million RBCs per microliter (mcL) or 4.5-5.5 x 1012/liter (L)
Women:	4.0-5.0 million RBCs per mcL or 4.0-5.0 x 1012/L
Children:	3.8-6.0 million RBCs per mcL or 3.8-6.0 x 1012/L
Newborn:	4.1-6.1 million RBCs per mcL or 4.1-6.1 x 1012/L

Hematocrit (HCT)
Men:	42%-52% or 0.42-0.52 volume fraction
Women:	36%-48% or 0.36-0.48 volume fraction
Children:	29%-59% or 0.29-0.59 volume fraction
Newborns:	44%-64% or 0.44-0.64 volume fraction

Hemoglobin (Hgb)
Men:	14-17.4 grams per deciliter (g/dL) or 140-174 grams per liter (g/L)
Women:	12-16 g/dL or 120-160 g/L
Children:	9.5-20.5 g/dL or 95-205 g/L
Newborn:	14.5-24.5 g/dL or 145-245 g/L

In general, a normal hemoglobin level is about one-third the value of the hematocrit.

Red blood cell indices
Mean corpuscular volume (MCV):	82-98 cubic millimeters (mm3) or 82-98femtoliters (fL)
Mean corpuscular hemoglobin (MCH):	26-34 picograms (pg) or 0.40-0.53 femtomoles (fmol)
Mean corpuscular hemoglobin concentration (MCHC):	32-36 grams per deciliter (g/dL) or 320-360 grams per liter (g/L)

Red cell distribution width (RDW)
Normal:	11.5%-14.5%

Platelet (thrombocyte) count
Adults:	140,000-400,000 platelets per mm3 or 140-400 x 109/L
Children:	150,000-450,000 platelets per mm 3 or 150-450 x 109/L

Mean platelet volume (MPV)
Adults:	7.4-10.4 mcm3 or 7.4-10.4 fL
Children:	7.4-10.4 mcm3 or 7.4-10.4 fL

Blood smear
Normal:	Blood cells are normal in shape, size, color, and number.

High values

Red blood cell (RBC)

Conditions that cause high RBC values include smoking, exposure to carbon monoxide, long-term lung disease, kidney disease, some cancers, certain forms of heart disease, alcoholism, liver disease, a rare disorder of the bone marrow (polycythemia vera), or a rare disorder of hemoglobin that binds oxygen tightly.
Conditions that affect the body’s water content can also cause high RBC values. These conditions include dehydration, diarrhea or vomiting, excessive sweating, severe burns, and the use of diuretics. The lack of fluid in the body makes the RBC volume look high; this is sometimes called spurious polycythemia.

White blood cell (WBC, leukocyte)

Conditions that cause high WBC values include infection, inflammation, damage to body tissues (such as a heart attack), severe physical or emotional stress (such as a fever, injury, or surgery), burns,kidney failure, lupus, tuberculosis (TB), rheumatoid arthritis, malnutrition, leukemia, and diseases such as cancer.
The use of corticosteroids, underactive adrenal glands, thyroid gland problems, certain medicines, or removal of the spleen can also cause high WBC values.

Platelets

High platelet values may be seen with bleeding, iron deficiency, some diseases like cancer, or problems with the bone marrow.

Low values

Red blood cell (RBC)

Anemia lowers RBC values. Anemia can be caused by heavy menstrual bleeding, stomach ulcers, colon cancer, inflammatory bowel disease, some tumors, Addison’s disease, thalassemia, lead poisoning,sickle cell disease, or reactions to some chemicals and medicines. A low RBC value may also be seen if the spleen has been taken out.
A lack of folic acid or vitamin B12 can also cause anemia, such as pernicious anemia, which is a problem with absorbing vitamin B12.
The RBC indices value and a blood smear may help find the cause of anemia.

White blood cell (WBC, leukocyte)

Conditions that can lower WBC values include chemotherapy and reactions to other medicines, aplastic anemia, viral infections, malaria, alcoholism, AIDS, lupus, or Cushing’s syndrome.
A large spleen can lower the WBC count.

Platelets

Low platelet values can occur in pregnancy or idiopathic thrombocytopenic purpura (ITP) and other conditions that affect how platelets are made or that destroy platelets.
A large spleen can lower the platelet count.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

If the elastic band was on your arm a long time while the blood sample was taken.
Taking medicines that can cause low platelet levels. Some examples of the many medicines that cause low platelet levels include steroids, some antibiotics, thiazide diuretics, chemotherapy medicines,quinidine, and meprobamate (Equanil, Miltown, Meprospan).
A very high white blood cell count or high levels of a type of fat (triglycerides). These can cause falsely high hemoglobin values.
Having an enlarged spleen, which may cause a low platelet count (thrombocytopenia) or a low white blood cell count. An enlarged spleen may be caused by certain types of cancer.
Pregnancy, which normally causes a low RBC value and less often a high WBC value.
Clumping of platelets in the test tube. This can cause a falsely low platelet count and occurs because of the substance used in the test tube

Cortisol in Blood

A cortisol test is done to measure the level of the hormone cortisol in the blood. The cortisol level may show problems with the adrenal glands or pituitary gland. Cortisol is made by the adrenal glands. Cortisol levels go up when the pituitary gland releases another hormone called adrenocorticotropic hormone (ACTH).

Cortisol has many functions. It helps the body use sugar (glucose) and fat for energy (metabolism), and it helps the body manage stress. Cortisol levels can be affected by many conditions, such as physical or emotional stress, strenuous activity, infection, or injury.

Normally, cortisol levels rise during the early morning hours and are highest about 7 a.m. They drop very low in the evening and during the early phase of sleep. But if you sleep during the day and are up at night, this pattern may be reversed. If you do not have this daily change (diurnal rhythm) in cortisol levels, you may have overactive adrenal glands. This condition is called Cushing’s syndrome.

Two blood samples may be taken: one in the morning and another in the afternoon.

Why It Is Done

A cortisol test is done to find problems of the pituitary gland or adrenal glands, such as making too much or too little hormones.

Results

A cortisol test is done to measure the level of the hormone cortisol in the blood.

Normal

Cortisol
Adult/Child	Morning	5-23 micrograms per deciliter (mcg/dL) or 138-635 nanomoles per liter (nmol/L)
Adult/Child	Afternoon	3-16 mcg/dL or 83-441 nmol/L
Newborn		2-11 mcg/dL or 55-304 nmol/L

High values

A high level of cortisol in the blood can mean Cushing’s syndrome, a disorder that can be caused by overactive adrenal glands, an adrenal gland tumor, some types of cancer, or long-term use of corticosteroids.
A high cortisol level can happen with Cushing’s disease, a condition caused by a noncancerous tumor of the pituitary gland (adenoma). An adenoma causes the pituitary gland to make too much of the hormone adrenocorticotropic hormone (ACTH), which in turn causes the adrenal glands to make too much cortisol.
A high blood cortisol level can be caused by severe liver or kidney disease, depression,hyperthyroidism, or obesity.
Pregnancy or birth control pills can also cause a high blood cortisol level.
Conditions such as recent surgery, illness, injury, or whole-body infection (sepsis) can cause high cortisol levels.

Low values

A low level of cortisol in the blood can mean Addison’s disease, which is caused by damage to the adrenal glands. If the pituitary gland is not working well, it can cause low levels of the hormone ACTH, which in turn causes low levels of cortisol. Conditions that can damage the adrenal glands or pituitary gland include some infections, head injury, and some autoimmune diseases.
A low level of cortisol can be caused by internal bleeding that leads to shock. For example, severe bleeding during childbirth that causes damage to the pituitary gland of the mother (Sheehan’s syndrome) can cause a low level of ACTH, which then leads to a low level of cortisol.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Having physical or emotional stress.
Being pregnant. This can cause urine cortisol levels to be high.
Having low blood sugar (hypoglycemia).
Eating, drinking, or exercising before the test.
Taking medicines, such as birth control pills, estrogen, amphetamines, or corticosteroids.
Having a radioactive scan within 1 week of a cortisol test.

Creatinine and Creatinine Clearance

Creatinine and creatinine clearance tests measure the level of the waste product creatinine in your blood and urine. These tests tell how well your kidneys are working. The substance creatine is formed when food is changed into energy through a process called metabolism. Creatine is broken down into another substance called creatinine, which is taken out of your blood by the kidneys and then passed out of your body in urine. See a picture of the kidneys.

Creatinine is made at a steady rate and is not affected by diet or by normal physical activities. If your kidneys are damaged and cannot work normally, the amount of creatinine in your urine goes down while its level in your blood goes up.

Three types of tests on creatinine can be done:

Blood creatinine level

The blood creatinine level shows how well your kidneys are working. A high creatinine level may mean your kidneys are not working properly. The amount of creatinine in the blood depends partly on the amount of muscle tissue you have; men generally have higher creatinine levels than women.

Creatinine clearance test

A creatinine clearance test measures how well creatinine is removed from your blood by your kidneys. A creatinine clearance test gives better information than a blood creatinine test on how well your kidneys are working. A creatinine clearance test is done on both a blood sample and on a sample of urine collected over 24 hours (24-hour urine sample).

Blood urea nitrogen-to-creatinine ratio (BUN:creatinine)

The levels of blood creatinine and blood urea nitrogen (BUN) can be used to find the BUN-to-creatinine ratio. A BUN-to-creatinine ratio can help your doctor check for problems, such as dehydration, that may cause abnormal BUN and creatinine levels.

Urea is a waste product made when protein is broken down in your body. Urea is made in the liver and passed out of your body in the urine. A blood urea nitrogen (BUN) test measures the amount of urea in your blood. Like creatinine, it can help your doctor see how well your kidneys are working.

Why It Is Done

A blood creatinine level or a creatinine clearance test is done to:

See if your kidneys are working normally.
See if your kidney disease is changing.
See how well the kidneys work in people who take medicines that can cause kidney damage.
Check for severe dehydration. Dehydration generally causes BUN levels to rise more than creatinine levels. This causes a high BUN-to-creatinine ratio. Kidney disease or blockage of the flow of urine from your kidney causes both BUN and creatinine levels to rise.

Results

Creatinine and creatinine clearance tests measure creatinine levels in your blood and urine to give information about how well your kidneys are working. The creatinine clearance value is found from the amounts of creatinine in the urine and blood and from the amount of urine you pass in 24 hours. This value is the amount of blood cleared of creatinine per minute, based on your body size.

Normal

Blood creatinine and creatinine clearance
Blood creatinine:	Men: 0.6-1.2 (mg/dL) or 71-106 (mcmol/L)Women: 0.4-1.0 mg/dL or 36-90 mcmol/L
Creatinine clearance:	Men (younger than 40 years): 107-139 (mL/min) or 1.8-2.3 milliliters per second (mL/sec)Women (younger than 40 years): 87-107 mL/min or 1.5-1.8 mL/secCreatinine clearance values normally go down as you get older (normal values go down by 6.5 mL/min for every 10 years past the age of 20).

BUN-to-creatinine ratio
Normal:	10:1 to 20:1

High values

High creatinine blood levels. High creatinine blood levels can mean serious kidney damage or disease is present. Kidney damage can be caused by a life-threatening infection, shock, cancer, or low blood flow to the kidneys. Other conditions that can cause high blood creatinine levels include blockage of theurinary tract (such as by a kidney stone), heart failure, dehydration, excessive blood loss that causes shock, gout, or muscle conditions (such as rhabdomyolysis, gigantism, acromegaly, myasthenia gravis,muscular dystrophy, and polymyositis). Usually a high blood creatinine level means that the creatinine clearance value is lower than normal.
High creatinine clearance. High creatinine clearance values can be caused by strenuous exercise, muscle injury (especially crushing injuries), burns, carbon monoxide poisoning, hypothyroidism, andpregnancy.
High BUN-to-creatinine ratio. High BUN-to-creatinine ratios occur with sudden (acute) kidney failure, which may be caused by shock or severe dehydration. A blockage in the urinary tract (such as a kidney stone) can cause a high BUN-to-creatinine ratio. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract.

Low values

Low blood creatinine levels. Low blood creatinine levels can mean lower muscle mass caused by a disease, such as muscular dystrophy, or by aging. Low levels can also mean some types of severe liver disease or a diet very low in protein. Pregnancy can also cause low blood creatinine levels.
Low creatinine clearance. Low creatinine clearance levels can mean serious kidney damage is present. Kidney damage can be from conditions such as a life-threatening infection, shock, cancer, low blood flow to the kidneys, or urinary tract blockage. Other conditions, such as heart failure, dehydration, and liver disease (cirrhosis), can also cause low creatinine clearance levels.
Low BUN-to-creatinine ratio. A low BUN-to-creatinine ratio may be linked with a diet low in protein, a severe muscle injury called rhabdomyolysis, pregnancy, cirrhosis, or syndrome of inappropriate antidiuretic hormone secretion (SIADH). SIADH sometimes occurs with lung disease, cancer, diseases of the central nervous system, and the use of certain medicines.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking medicines, such as methyldopa, trimethoprim (Proloprim, Trimpex), vitamin C (ascorbic acid), cimetidine (Tagamet), some diuretics, and cephalosporin antibiotics, especially cefoxitin (Mefoxin). These affect the blood creatinine levels.
Taking medicines, such as vitamin C (ascorbic acid), phenytoin (Dilantin), some cephalosporin antibiotics, captopril, aminoglycosides, trimethoprim (Proloprim, Trimpex), cimetidine (Tagamet),quinine, quinidine (Cardioquin, Quinaglute, Quinidex), procainamide, and the antifungal medication amphotericin B. These affect the creatinine clearance levels.
Taking medicines, such as cimetidine (Tagamet), steroids, and tetracycline antibiotics. These can affect the BUN-to-creatinine ratio.
Not collecting all your urine during the 24-hour urine collection test.
Doing strenuous exercise 2 days before creatinine clearance test.
Eating more than 8 oz (227 g) of meat, especially beef, in the 24 hours before a blood creatinine test and during a creatinine clearance urine test.

Dehydroepiandrosterone

Dehydroepiandrosterone (DHEA) is an endogenous hormone (made in the human body), and secreted by the adrenal gland. DHEA serves as precursor to male and female sex hormones (androgens and estrogens). DHEA levels in the body begin to decrease after age 30, and are reported to be low in some people with anorexia, end-stage kidney disease, type 2 diabetes (non-insulin dependent diabetes), AIDS, adrenal insufficiency, and in the critically ill. DHEA levels may also be depleted by a number of drugs, including insulin, corticosteroids, opiates, and danazol.

There is sufficient evidence supporting the use of DHEA in the treatment of adrenal insufficiency, depression, induction of labor, and systemic lupus erythematosus.

No studies on the long-term effects of DHEA have been conducted. DHEA can cause higher than normal levels of androgens and estrogens in the body, and theoretically may increase the risk of prostate, breast, ovarian, and other hormone-sensitive cancers. Therefore, it is not recommended for regular use without supervision by a licensed health professional.

Estrogens

An estrogen test measures the level of the most important estrogen hormones (estradiol, estriol, and estrone) in a blood or urine sample.

Estradiol is the most commonly measured type of estrogen for nonpregnant women. The amount of estradiol in a woman’s blood varies throughout her menstrual cycle. After menopause, estradiol production drops to a very low but constant level.
Estriol levels usually are only measured during pregnancy. Estriol is produced in large amounts by theplacenta, the tissue that links the fetus to the mother. It can be detected as early as the 9th week of pregnancy, and its levels increase until delivery. Estriol can also be measured in urine.
Estrone may be measured in women who have gone through menopause to determine their estrogen levels. It also may be measured in men or women who might have cancer of the ovaries, testicles, oradrenal glands.

Both men and women produce estrogen hormones. Estrogens are responsible for female sexual development and function, such as breast development and the menstrual cycle. In women, estrogens are produced mainly in the ovaries and in the placenta during pregnancy. Small amounts are also produced by the adrenal glands. In men, small amounts of estrogens are produced by the adrenal glands and testicles. Small amounts of estrone are made throughout the body in most tissues, especially fat and muscle. This is the major source of estrogen in women who have gone through menopause.

Why It Is Done

A test for estrogen is done to:

Help detect fetal birth defects (especially Down syndrome) during pregnancy. When the test for estriol is combined with alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG), it is called a triple screen test. When the amount of a hormone called inhibin A is also measured along with estriol, AFP, and hCG, the test is called a quad marker screen. Other blood tests and fetal ultrasound may be done as well.
Evaluate estrogen-producing tumors of the ovaries in girls before menstruation starts and in women after menopause.
Explain abnormal sexual characteristics in men, such as enlarged breasts (gynecomastia). This test can also help detect the presence of estrogen-producing tumors growing in the testicles.

Results

An estrogen test measures the level of the most important estrogen hormones (estradiol, estriol, and estrone) in a blood or urine sample.
Results are usually available within 24 hours.

Normal

For girls and women between puberty and menopause, estrogen levels vary throughout the menstrual cycle.
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, Dr. Houston will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Estradiol levels in blood
Women before menopause:	20-750 (pg/mL)
Women after menopause:	Less than or equal to 20 pg/mL
Men:	10-50 pg/mL
Children:	Less than 15 pg/mL
Estriol in pregnant women
1st trimester:	Less than 38 nanograms per milliliter (ng/mL)
2nd trimester:	38-140 ng/mL
3rd trimester:	31-460 ng/mL

Many conditions can change estrogen levels. Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.

High values

High values may be caused by:

Ovarian stimulation used to treat infertility (for example, before in vitro fertilization).
Cancer, such as cancer of the ovaries, testicles, or adrenal glands.
Serious liver disease (cirrhosis).
A pregnancy with more than one fetus, such as twins or triplets.
Early (precocious) puberty.

Low values

Low values may be caused by:

Problems with ovarian function, which can be caused by a failure of an ovary to develop properly (Turner’s syndrome) or because of a drop in pituitary gland activity.
Anorexia nervosa.
Menopause.
A problem with the fetus or placenta during pregnancy.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Hormone replacement therapy after menopause.
Birth control pills, patches, or rings and other forms of hormonal birth control.
Having a test that uses a radioactive substance, such as a bone scan, within 1 week before the test.
Medicines, such as clomiphene or steroids (for example, prednisone).
High levels of sugar in the urine caused by diabetes.

Follicle-Stimulating Hormone

A follicle-stimulating hormone test measures the amount of follicle-stimulating hormone (FSH) in a bloodsample. FSH is produced by the pituitary gland.

In women, FSH helps control the menstrual cycle and the production of eggs by the ovaries. The amount of FSH varies throughout a woman’s menstrual cycle and is highest just before she releases an egg (ovulates).
In men, FSH helps control the production of sperm. The amount of FSH in men normally remains constant.

The amounts of FSH and other hormones (luteinizing hormone, estrogen, and progesterone) are measured in both a man and a woman to determine why the couple cannot become pregnant (infertility). The FSH level can help determine whether male or female sex organs (testicles or ovaries) are functioning properly.

Why It Is Done

A follicle-stimulating hormone (FSH) test may be done to:

Help find the cause of infertility. FSH testing is commonly used to help evaluate a:
- Woman’s egg supply (ovarian reserve).
- Man’s low sperm count.
Help evaluate menstrual problems, such as irregular or absent menstrual periods (amenorrhea). This can help determine whether the woman has gone through menopause.
Determine if a child is going through early puberty (also called precocious puberty). Puberty is early when it starts in girls younger than age 9 and in boys younger than age 10.
Determine why sexual features or organs are not developing when they should (delayed puberty).
Help diagnose certain pituitary gland disorders, such as a tumor

Results

A follicle-stimulating hormone test measures the amount of follicle-stimulating hormone (FSH) in a blood sample. The test results depend on your age and stage of sexual development.

The phase of a woman’s menstrual cycle can affect results, so it is important to know the first day of your last menstrual period at the time the test is performed.

Results are usually available within 24 hours.

Normal

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Follicle-stimulating hormone (FSH)
Menstruating women
Follicular phase:	2-15 international units per liter (IU/L)
Midcycle peak:	22-57 IU/L
Luteal phase:	1-16 IU/L
Women past menopause:	14-52 IU/L
Men:	1-8 IU/L
Children before puberty:	0.5-4 IU/L

Many conditions can change FSH levels. Dr. Houston will discuss any significant abnormal results with you in relation to your symptoms and past health.

High values

High FSH values in a woman may mean:

Loss of ovarian function before age 40 (ovarian failure).
Menopause has occurred.

High FSH values in a man may mean:

Klinefelter syndrome.
Testicles are absent or not functioning properly.
Testicles have been damaged by a disease, such as alcohol dependence, or by treatments, such as X-rays or chemotherapy.

High values in children may mean that puberty is about to start.

Low values

Low FSH values may mean:

A woman is not producing eggs (prevents ovulation) or a man is not producing sperm.
An area of the brain (the hypothalamus or pituitary gland) is not functioning properly.
A tumor is present that interferes with the brain’s ability to control FSH production.
Stress.
Starvation or being very underweight.

What Affects the Test

Results of the follicle-stimulating hormone (FSH) test may be affected by:

The use of hormones, such as testosterone, estrogen, and progesterone (including birth control pills).
Heavy cigarette smoking.
Age.
The use of medicines, such as cimetidine, clomiphene, digitalis, and levodopa. Make sure your doctor has a complete list of all the prescription and over-the-counter medicines you are taking, including herbs and natural substances.
Having a test such as a thyroid scan or bone scan that uses a radioactive substance within 1 week of the FSH test.

Glycohemoglobin (HbA1c, A1c)

Glycohemoglobin is a blood test that checks the amount of sugar (glucose) bound to hemoglobin. Normally, only a small percentage of hemoglobin in the blood (4% to 6%) has glucose bound to it. People who havediabetes or other conditions that increase their blood glucose levels have more glycohemoglobin than normal.

The glycohemoglobin A1c is used to diagnose diabetes. The glycohemoglobin A1c test checks the long-term control of blood glucose levels in people with diabetes. Most doctors think the glycohemoglobin A1c level is the best way to check how well a person is controlling his or her diabetes.

A home blood glucose test measures the level of blood glucose only at that moment. Blood glucose levels change during the day because of diet, exercise, and the level of insulin in the blood.

It is useful for a person who has diabetes to have information about the long-term control of blood sugar levels. The glycohemoglobin test is one blood sample every 3 to 4 months, and the test does not change with any recent changes in diet, exercise, or medicines.

Glucose binds to hemoglobin in red blood cells at a steady rate. Since red blood cells last 3 to 4 months, the glycohemoglobin A1c test shows how much glucose is in the plasma part of blood. This test shows how well your diabetes has been controlled in the last 2 to 3 months and whether your diabetes medicine needs to be changed.

The A1c level can also help your doctor see how big your risk is of developing problems from diabetes, such as kidney failure, vision problems, and leg or foot numbness. The lower your A1c level, the lower your chance for problems.

Why It Is Done

This test is done to:

Diagnose diabetes.
Check your treatment for diabetes.

Results

Glycohemoglobin is a blood test that checks the amount of sugar (glucose) bound to hemoglobin. The result is shown as a percentage. The result of your A1c test can also be used to estimate your average blood sugar level. This is called your estimated average glucose, or eAG. Your A1c level may be reported without a total glycohemoglobin value. Your doctor will have your test results in 1 to 2 days.

Normal

The American Diabetes Association (ADA) uses the following A1c levels to identify diabetes categories:1

Glycohemoglobin A1c
Normal	Less than 5.7%
Prediabetes (increased risk for diabetes)	5.7%-6.4%
Diabetes	6.5% and higher

The ADA recommends that adults with diabetes have an A1c level less than 7%. If your A1c level is higher than 7%, you may need changes in your diabetes treatment.2 Talk to Dr. Houston about your diabetes treatment plan and goals.

A1c and estimated average glucose (eAG)
A1c %	Estimated average plasmaglucose (mg/dL)	Estimated average plasma glucose (mmol/L)
6%	126	7.0
7%	154	8.6
8%	183	10.2
9%	212	11.8
10%	240	13.4
11%	269	14.9
12%	298	16.5

A1c recommendations for children and teens
Age	A1c %
Children younger than 6 years old	Less than 8.5%
Children ages 6-12 years old	Less than 8%
Teens ages 13-19 years old	Less than 7.5%

High values

A glycohemoglobin A1c level higher than the level that is listed in the table above means that your diabetes has been poorly controlled over the last 2 to 3 months.

Some medical conditions can increase A1c levels, but the results may still be within a normal range. These conditions include Cushing’s syndrome, pheochromocytoma, and polycystic ovary syndrome (PCOS).

Corticosteroid treatment increases the A1c level.

A1c levels may be higher in children and adolescents with diabetes.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Having severe blood loss or a blood transfusion in the last 3 months.
Having certain medical conditions, such as sickle cell anemia, hemolytic anemia, some types ofthalassemia, and severe kidney disease.
Having your spleen taken out. This changes the normal life cycle of red blood cells and A1c levels.

Homocysteine

A homocysteine test measures the amount of the amino acid homocysteine in the blood.

Why It Is Done

A homocysteine blood test is done to:

Help identify vitamin B12 deficiency or folic acid deficiency. But other tests for these deficiencies are available.
Help identify a rare inherited disease (homocystinuria) that causes a deficiency of one of several enzymes needed to convert food to energy.
Help determine a cause for otherwise unexplained blood clots.

Results

A homocysteine test measures the amount of the amino acid homocysteine in the blood.

Results are ready in 24 hours.

Normal

Homocysteine
Normal:	0.54-2.3 mg/L	4-17 (mcmol/L)

Many conditions can affect homocysteine levels. Dr. Houston will discuss any significant abnormal results with you in relation to your symptoms and past health.

High values

High values of homocysteine may be caused by:

Not getting enough folic acid, vitamin B6, or vitamin B12 in your diet.
Other conditions or diseases, such as homocystinuria, kidney disease, hypothyroidism, Alzheimer’s disease, or certain cancers.
Using too much alcohol.
Your sex. Homocysteine levels are normally higher in men than in women.
Age. Homocysteine levels get higher as you get older.

Low values

Low values of homocysteine may be caused by some medicines or vitamins such as daily folic acid, vitamin B12, or niacin.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Going through menopause.
Having high blood pressure (hypertension).
Smoking or other tobacco use.
Having a family history of high homocysteine levels.
Drinking more than 2 to 3 cups of coffee a day over many years.
Taking medicines, such as anticonvulsants, antibiotics, and birth control pills.
Having kidney disease, certain forms of leukemia, or psoriasis.
Having a rare family (inherited) disease that causes the lack of an enzyme needed to prevent the build up of homocysteine in the blood (homocystinuria).

Liver Function Tests

Liver function tests (LFTs) are a group of blood tests that detect inflammation and damage to the liver. They can also check how well the liver is working. Liver function testing includes ALT, AST, alkaline phosphatase, PT, INR, albumin, and bilirubin.

Why Check Liver Function?

Most often, a liver function test panel is ordered as a routine lab test. Many doctors check liver function in new patients or during annual physicals.

Your doctor may conduct an LFT if:

You are taking a medication that can harm the liver.
You have liver disease.
You have symptoms of liver or bile system disease (abdominal pain, nausea and vomiting, or yellow skin).
You drink alcohol excessively.

Liver function tests may be done together in a panel or tested separately.

Liver Function Tests: ALT and AST

The liver filters and processes blood as it circulates through the body. It metabolizes nutrients, detoxifies harmful substances, makes blood clotting proteins, and performs many other vital functions. The cells in the liver contain proteins called enzymes that drive these chemical reactions.

When liver cells are damaged or destroyed, the enzymes in the cells leak out into the blood, where they can be measured by blood tests. Liver function tests check the blood for two main liver enzymes:

Aspartate aminotransferase (AST), sometimes called SGOT. The AST enzyme is also found in muscles and many other tissues besides the liver.
Alanine aminotransferase (ALT), sometimes called SGPT. ALT is almost exclusively found in the liver.

If ALT and AST are found together in elevated amounts in the blood, liver damage is most likely present.

Liver Function Tests: Alkaline Phosphatase, 5′ Nucleotidase, and GGT

Another of the liver’s key functions is the production of bile, which helps digest fat. Bile flows through the liver in a system of small tubes (ducts), and is eventually stored in the gallbladder, under the liver.

When bile flow is slow or blocked, blood levels of certain liver enzymes rise:

Alkaline phosphatase
5′ nucleotidase
Gamma-glutamyl transpeptidase (GGT)

Liver function tests may check for any or all of these enzymes in the blood. Alkaline phosphatase is by far the most commonly tested of the three.

If alkaline phosphatase and/or 5′ nucleotidase and GGT are elevated, a problem with bile flow is most likely present. Bile flow problems can be due to a problem in the liver, the gallbladder, or the tubes connecting them.

Liver Function Tests: PT and INR

Besides its functions in metabolism, the liver makes proteins that are essential to normal blood clotting. Certain LFTs check the liver’s ability to make these proteins:

Prothrombin time: A test of the time it takes for a blood sample to clot, under specific conditions in a lab. If low levels of clotting factors are present, the prothrombin time is longer.
International normalized ratio (INR): Not a test, but a standardized way for all labs to report PT, so their results can be compared accurately with each other.

PT and INR rise in people with severe liver disease because the liver fails to make normal amounts of certain clotting factors. An elevated PT can have many other causes besides liver disease, however.

PT is often checked together with PTT (partial thromboplastin time), which is not a liver function test. If PT and/or PTT are elevated, a problem with bleeding or clotting may be present.

Liver Function Tests: Albumin

The liver also makes albumin, an essential protein that circulates in blood. Albumin levels are low in people with severe chronic liver disease, because the liver does not make normal amounts of albumin. However, albumin levels may fall in a variety of medical conditions. A low albumin level is often temporary, and does not make a diagnosis of liver disease.

Liver Function Tests: Bilirubin

Bilirubin is a waste product from the breakdown of red blood cells. The liver processes bilirubin so it can be excreted in stool. Bilirubin flows through the liver’s bile ducts, dissolved in bile.

Bilirubin blood levels may be elevated in people with impaired bile flow. This can occur in severe liver disease, gallbladder disease, or other bile system conditions. Very high bilirubin levels cause jaundice, in which the skin and whites of the eyes turn yellow. Bilirubin can be a useful liver function test in people with a known bile flow problem. An elevated bilirubin may also be present in people with a type of anemia, called hemolytic anemia.

Luteinizing Hormone

A luteinizing hormone test measures the amount of luteinizing hormone (LH) in a sample of blood or urine. LH is produced by the pituitary gland.

In women, LH helps regulate the menstrual cycle and egg production (ovulation). The level of LH in a woman’s body varies with the phase of the menstrual cycle. It increases rapidly just before ovulationoccurs, about midway through the cycle (day 14 of a 28-day cycle). This is called an LH surge.Luteinizing hormone and follicle-stimulating hormone levels rise and fall together during the monthly menstrual cycle.
In men, LH stimulates the production of testosterone, which plays a role in sperm production.

Why It Is Done

A luteinizing hormone (LH) test may be done to:

Help find the cause for a couple’s inability to become pregnant (infertility). LH testing is commonly used to help evaluate:
- A woman’s egg supply (ovarian reserve).
- A man’s sperm count.
Help evaluate menstrual problems, such as irregular or absent menstrual periods (amenorrhea). This can help determine if the woman has gone through menopause.
Determine if a child is going through early puberty (also called precocious puberty). Puberty is early when it starts in girls younger than age 9 and in boys younger than age 10.
Determine why sexual features or organs are not developing when they should (delayed puberty).
Determine (usually with a urine sample) when a woman is ovulating. Home urine tests for ovulation are available.
Monitor a woman’s response to medicines given to stimulate ovulation.

Results

A luteinizing hormone test measures the amount of luteinizing hormone (LH) in a sample of blood or urine.
LH levels depend on a person’s age and stage of sexual development, and, in a woman, on the phase of hermenstrual cycle. The urine test to determine whether a woman is ovulating detects only the presence (positive result) or absence (negative result) of LH.

Normal

Luteinizing hormone in blood
Menstruating women
Follicular phase:	1-10 international units per liter (IU/L)
Midcycle peak:	6-17 IU/L
Luteal phase:	1-9 IU/L
Women past menopause:	19-100 IU/L
Men:	1-15 IU/L
Male children at puberty:	4-12 IU/L
Female children at puberty	2-14 IU/L

Luteinizing hormone in urine Most home urine tests to predict ovulation determine only the presence of LH (called qualitative testing) and not the specific level or quantity. Home urine test results are either “positive” (LH is present) or “negative” (LH is not present).

Many conditions can change LH levels. Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.

High values

High luteinizing hormone values in a woman may mean:

Ovaries are absent or have been removed.
Ovaries are not functioning because of menopause, polycystic ovary syndrome (PCOS), or damage from chemotherapy.
Early puberty in young girls.

High luteinizing hormone values in a man may mean:

Testicles are absent or have been removed.
Testicles are not functioning because of surgery or damage from mumps, X-ray exposure, chemotherapy, cancer, or injury.
Klinefelter syndrome.

Low values

Low luteinizing hormone values in a man or woman may mean:

Anorexia nervosa.
Pituitary gland failure.
Damage to a part of the brain called the hypothalamus.
Stress.
Low body weight.

What Affects the Test

Results of the luteinizing hormone test may be affected by:

The use of certain hormones, including those containing estrogen or progesterone (such as birth control pills).
The use of medicines, such as clomiphene, spironolactone, naloxone, digoxin, phenothiazine, and those given for seizures (anticonvulsants).
Obesity.
Hyperthyroidism.
Liver disease.
Diagnostic imaging procedures, such as a thyroid scan or bone scan, that use a radioactive substance (tracer) and were performed within 7 days prior to LH testing.

Magnesium (Mg)

A magnesium test checks the level of magnesium in the blood. Magnesium is an important electrolyteneeded for proper muscle, nerve, and enzyme function. It also helps the body make and use energy and is needed to move other electrolytes (potassium and sodium) into and out of cells.

Most of the magnesium in the body is found in the bones and inside the cells. Only a tiny amount of magnesium is normally present in the blood.

Tests for other electrolytes, such as calcium, potassium, sodium, and phosphorus, may be done along with a test for magnesium.

Why It Is Done

A test for magnesium is done to:

Find a cause for nerve and muscle problems, such as muscle twitches, irritability, and muscle weakness.
Find the cause of symptoms such as low blood pressure, nausea, vomiting, diarrhea, dizziness, muscle weakness, and slurred speech.
Monitor kidney function.
Find the cause of heart problems or trouble breathing, especially in people who have kidney disease.
Find the cause of a low calcium or potassium level that is not improving with treatment.
Look for changes in magnesium levels caused by medicines, such as diuretics.
See if people with heart problems need extra magnesium. Low magnesium levels can increase the chances of life-threatening heart rhythm problems.

Results

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Normal

Magnesium blood level
Adult:	1.8-2.6 (mEq/L) or 0.74-1.07 (mmol/L)

Many conditions can change magnesium levels. Dr. Houston will talk with you about any abnormal results that may be related to your symptoms and past health.

What Affects the Test

High values

High magnesium levels may be caused by:

Dehydration.
Diseases of the adrenal glands, such as Addison’s disease.
An overactive parathyroid gland (hyperparathyroidism).
An underactive thyroid gland (hypothyroidism).
Kidney failure.
The use of medicine that contains magnesium, such as antacids and laxatives.

Low values

Low magnesium levels may be caused by:

Alcohol abuse or withdrawal.
Complications from diabetes, such as diabetic ketoacidosis.
Diseases that block with the way food is absorbed in the intestines, such as sprue.
High blood calcium levels (hypercalcemia).
Infection and swelling of the pancreas (pancreatitis).
Kidney disease.
Long-term diarrhea.
Not getting enough magnesium in the foods you eat.
Pregnancy, especially in the second or third trimester.
Underactive parathyroid glands (hypoparathyroidism).

Microalbumin Urine Test

A microalbumin test checks urine for the presence of a protein called albumin. Albumin is normally found in the blood and filtered by the kidneys. When the kidneys are working properly, albumin is not present in the urine. But when the kidneys are damaged, small amounts of albumin leak into the urine. This condition is called microalbuminuria.

Microalbuminuria is most often caused by kidney damage from diabetes. But many other conditions can lead to kidney damage, such as high blood pressure, heart failure, cirrhosis, or systemic lupus erythematosus (SLE). If early kidney damage is not treated, larger amounts of albumin and protein may leak into the urine. This condition is called macroalbuminuria or proteinuria. When the kidneys spill protein, it can mean serious kidney damage is present. This can lead to chronic kidney disease. A microalbumin urine test can be done on a sample of urine collected randomly (usually after the first time you urinate in the morning), a sample collected over a 24-hour period, or a sample collected over a specific period of time, such as 4 hours or overnight.

Why It Is Done

A microalbumin urine test is done to check for protein (albumin) in the urine. Early detection may change treatment in an effort to preserve as much kidney function as possible.

Results

A microalbumin test checks urine for the presence of a protein called albumin. Microalbuminuria is most often caused by kidney damage from diabetes.

Normal results may vary depending on:

The laboratory.
The type (random versus timed) of urine sample collected.
The time of day of the sample.
Whether you are male or female.
Whether you are on bed rest or able to move about normally.

Albumin in urine
Normal:	Less than 30 milligrams (mg) of albumin in 24 hoursLess than 20 milligrams per liter (mg/L) for 10-hour (overnight) collection

Higher-than-normal values

You may need more than one test to find out how well your kidneys are working.

If your results are higher than normal, Dr. Houston may check your urine more often to watch for kidney damage.
If you have 2 or 3 high results in a 3- to 6-month period and you have diabetes, your doctor may find kidney damage (diabetic nephropathy). Even though diabetes is the most common reason for high results, there are many other kidney problems that can cause high results.

Pregnant women with diabetes may have their urine checked to watch for high amounts of albumin.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Having high blood sugar levels, urinary tract infections, high blood pressure, heart failure, or a high feverduring an infection.
Exercising just before the test.
Taking medicines, such as aspirin, corticosteroids, or some antibiotics, such as amoxicillin.
Having menstrual bleeding or vaginal discharge, which may temporarily affect the urine sample.

Phosphate in Blood

A phosphate test measures the amount of phosphate in a blood sample. Phosphate is a charged particle (ion) that contains the mineral phosphorus. The body needs phosphorus to build and repair bones and teeth, help nerves function, and make muscles contract. Most (about 85%) of the phosphorus contained in phosphate is found in bones. The rest of it is stored in tissues throughout the body.

The kidneys help control the amount of phosphate in the blood. Extra phosphate is filtered by the kidneysand passes out of the body in the urine. A high level of phosphate in the blood is usually caused by a kidney problem.

The amount of phosphate in the blood affects the level of calcium in the blood. Calcium and phosphate in the body react in opposite ways: As blood calcium levels rise, phosphate levels fall. But this relation between calcium and phosphate may be disrupted by some diseases or infections. For this reason, phosphate and calcium levels are usually measured at the same time.

Why It Is Done

A test to measure phosphate in blood may be done to:

Check phosphate levels if you have kidney disease or bone disease.
Help find problems with certain glands, such as the parathyroid glands.

Results

A phosphate test measures the amount of phosphate in a blood sample. Phosphate is a charged particle (ion) that contains the mineral phosphorus. Phosphate levels are usually higher in children than in adults because of the active bone growth occurring in children.

Normal

Phosphate in blood
	Milligrams per deciliter (mg/dL)	Millimoles per liter (mmol/L)
Adults:	2.7-4.5	0.87-1.45
Children:	4.5-5.5	1.45-1.78
Newborns:	4.5-9.0	1.45-2.91

High values

High phosphate levels may be caused by:

Kidney disease, underactive parathyroid glands (hypoparathyroidism), acromegaly, rhabdomyolysis, healing fractures, untreated diabetic ketoacidosis, or certain bone diseases.
Too much vitamin D in the body.
A decrease in magnesium levels.
Pregnancy.

Low values

Low phosphate levels may be caused by:

Hyperparathyroidism, certain bone diseases (such as osteomalacia), lack of vitamin D, severe burns, or some kidney or liver diseases.
Severe malnutrition or starvation.
A condition such as sprue that prevents the intestines from absorbing nutrients properly.
Alcohol dependence.
High calcium levels.

What Affects the Test

Results from a blood phosphate test may be affected by:

Drinking alcohol before the test.
Using some medicines that can increase phosphate levels, such as androgen hormones, anabolic steroids, and enemas that contain phosphate.
Taking too much vitamin D.
Using some medicines that can decrease phosphate levels, such as antacids, insulin, acetazolamide, and epinephrine. A large infusion of sugar (glucose) that causes insulin levels to increase can also decrease phosphate levels.
Having a disease, such as lymphoma, that causes calcium levels to rise or fall.
Having a rare disease, such as diabetes insipidus, that causes the kidneys to produce large amounts of urine.

Potassium (K) in Blood

A potassium test checks how much potassium is in the blood. Potassium is both an electrolyte and a mineral. It helps keep the water (the amount of fluid inside and outside the body’s cells) and electrolyte balance of the body. Potassium is also important in how nerves and muscles work.

Potassium levels often change with sodium levels. When sodium levels go up, potassium levels go down, and when sodium levels go down, potassium levels go up. Potassium levels are also affected by a hormone called aldosterone, which is made by the adrenal glands.

Potassium levels can be affected by how the kidneys are working, the blood pH, the amount of potassium you eat, the hormone levels in your body, severe vomiting, and taking certain medicines, including potassium supplements. Certain cancer treatments that destroy cancer cells can also make potassium levels high.

Many foods are rich in potassium, including scallops, potatoes, figs, bananas, prune juice, orange juice, and squash. A balanced diet has enough potassium for the body’s needs. But potassium is passed in the urine even if the level in the blood is low so the level of potassium in the body can get lower.

A potassium level that is too high or too low can be serious. Abnormal potassium levels may cause symptoms such as muscle cramps or weakness, nausea, diarrhea, frequent urination, dehydration, low blood pressure, confusion, irritability, paralysis, and changes in heart rhythm.

Other electrolytes, such as sodium, calcium, chloride, magnesium, and phosphate, may be checked in a blood sample at the same time as a blood test for potassium.

Why It Is Done

A blood test to check potassium is done to:

Check levels in people being treated with medicines such as diuretics and for people having kidney dialysis.
Check to see whether treatment for too low or too high potassium levels is working.
Check people with high blood pressure who may have a problem with their kidneys or adrenal glands.
Check the effects of extra nutrition (total parenteral nutrition [TPN]) on potassium levels.
Check to see whether certain cancer treatments are causing too many cells to be destroyed (cell lysis). Cell lysis syndrome causes very high levels of some electrolytes, including potassium.

Results

A potassium test checks how much potassium is in the blood. Potassium is an electrolyte and mineral.

Blood potassium levels also vary with age.

Results are ready in 1 day.

Potassium (K)
Adults:	3.5-5.2 milliequivalents per liter (mEq/L) or 3.5-5.2 millimoles per liter (mmol/L)
Children:	3.4-4.7 mEq/L or 3.4-4.7 mmol/L
Infants:	4.1-5.3 mEq/L or 4.1-5.3 mmol/L
Newborns:	3.7-5.9 mEq/L or 3.7-5.9 mmol/L

Many conditions can affect potassium levels. Dr. Houston will talk with you about any abnormal results that may be related to your symptoms and past health.

High values

High blood potassium levels may be caused by damage or injury to the kidneys. This prevents the kidneys from removing potassium from the blood normally.
High blood potassium levels can also be caused by conditions that move potassium from the body’s cells into the blood. These conditions include severe burns, crushing injuries, heart attack, and diabetic ketoacidosis.
Taking too many potassium supplements can also cause high levels of potassium in the blood.
Too much acid (pH) in the blood makes potassium levels higher by causing the potassium in the body’s cells to “leak” out of cells and into the blood.
Some medicines, such as angiotensin-converting enzyme (ACE) inhibitors, can cause high potassium levels.

Low values

Low blood potassium levels can be caused by high levels of aldosterone (hyperaldosteronism) made by the adrenal glands.
Other conditions that can cause low blood potassium levels include severe burns, cystic fibrosis,alcoholism, Cushing’s syndrome, dehydration, malnutrition, vomiting, diarrhea and certain kidney diseases, such as Bartter’s syndrome. Bartter’s syndrome is a condition characterized by enlargement of certain kidney cells. It is more common in children and may be associated with an abnormally short stature (dwarfism). The cause of Bartter’s syndrome is not fully known.
Medicines, such as diuretics, are a common cause of low potassium levels.

Prostate-Specific Antigen (PSA)

A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood. PSA is released into a man’s blood by his prostate gland. Healthy men have low amounts of PSA in the blood. The amount of PSA in the blood normally increases as a man’s prostate enlarges with age. PSA may increase because of inflammation of the prostate gland (prostatitis) or prostate cancer. An injury, a digitalrectal exam, or sexual activity (ejaculation) may also briefly raise PSA levels.

Prostate cancer often grows very slowly, without causing major problems. Finding prostate cancer early and treating it may prevent some health problems and reduce the risk of dying from the cancer. But some treatments for prostate cancer can cause other problems, such as being unable to control urination (incontinence) or erection problems (erectile dysfunction). Some men may choose not to have a PSA test or treat prostate cancer if it is found. For example, a man older than age 75 who has no bothersome symptoms of prostate cancer may choose not to treat the cancer if it is found, so he would not need a PSA test.

Why It Is Done

The prostate-specific antigen (PSA) test is done to:

Screen men for prostate cancer. Experts agree that PSA testing is not right for all men. If a PSA test is used for screening, it is usually done for men older than age 50 or for those at high risk for prostate cancer, such as men with a family history of prostate cancer, or for African-American men who have a higher chance of developing cancer than other men. Since other common medical conditions, such asbenign prostatic hyperplasia (BPH) and prostatitis, can cause high PSA levels, a prostate biopsy is needed to confirm a diagnosis of cancer.
Check if cancer may be present when results from other tests, such as a digital rectal exam, are not normal. A PSA test does not diagnose cancer, but it can be used along with other tests to determine if cancer is present.

Watch prostate cancer during active surveillance or other treatment. If PSA levels increase, the cancer may be growing or spreading. PSA is usually not present in a man who has had his prostate gland removed. A PSA level that rises after prostate removal may mean the cancer has returned or has spread.

Results

A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood.

Normal

Because normal PSA levels seem to increase with age, age-specific ranges may be used. But the use of age-specific ranges is controversial, and some doctors prefer to use one range for all ages. For this reason, it is important to discuss your test results with Dr. Houston.

Total prostate-specific antigen (PSA)
Men age 40-49:	0-2.5 nanograms per milliliter (ng/mL)	0-2.5 micrograms per liter (mcg/L)
Men age 50-59:	0-3.5 ng/mL	0-3.5 mcg/L
Men age 60-69:	0-4.5 ng/mL	0-4.5 mcg/L
Men 70-79:	0-6.5 ng/mL	0-6.5 mcg/L

High values

High levels do not always mean prostate cancer is present. PSA levels may be high if the prostate gland is enlarged (benign prostatic hyperplasia, or BPH) or inflamed (prostatitis).
PSA levels above 8.0 ng/mL (or 8.0 mcg/L) may mean prostate cancer. A transrectal ultrasound (TRUS)and prostate biopsy are needed to confirm a diagnosis of cancer.

A follow-up test that measures free prostate-specific antigen (free PSA) may be used to see if a prostate biopsy should be done to check for cancer. Free PSA is prostate-specific antigen that is not attached to proteins in the blood. The lower a man’s free PSA level, the more likely he is to develop prostate cancer.

Free prostate-specific antigen (fPSA)
Percent free PSA	Probability of cancer
More than 25%:	8%
20%-25%:	16%
15%-20%:	20%
10%-15%:	28%
0%-10%:	56%

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Recent sexual activity (ejaculation).
Recent use of a tube (catheter) to drain urine or a cystoscopy.
Recent urinary tract infection (UTI) or prostatitis.
Recent digital rectal exam, prostate biopsy, or prostate surgery.
Large doses of medicines, such as cyclophosphamide (Cytoxan) and methotrexate for cancer treatment.
The medicines finasteride (Proscar) and dutasteride (Avodart), which are used to prevent further enlargement of the prostate gland in men with BPH.

Renin Assay

A renin assay blood test is done to find the cause of high blood pressure (hypertension). Renin is an enzymemade by special cells in the kidneys. Renin works with aldosterone (a hormone made by the adrenal glands) and several other substances to help balance sodium and potassium levels in the blood and fluid levels in the body, which affects your blood pressure.

A renin test is often done at the same time as an aldosterone test. In some people, it may be normal to have high blood levels of both renin and aldosterone. If renin levels are low and aldosterone levels are high, a tumor may be present in the adrenal glands.

Why It Is Done

A renin test is done to find the cause of high blood pressure (hypertension), especially when potassium levels in the blood are low.

Results

A renin assay blood test is done to find the cause of high blood pressure (hypertension). The time of day and your position (standing, sitting, or lying down) before the blood sample is collected, your age, and the level of sodium in your blood all affect the test results.

Normal

Plasma renin activity
Adult (upright position, normal-sodium diet)	0.7-3.3 nanograms per milliliter per hour (ng/mL/hr) or 0.7-3.3micrograms per liter per hour (mcg/L/hr)
Adult (lying down, normal-sodium diet)	0.2-1.6 ng/mL/hr or 0.2-1.6 mcg/L/hr
Adult (upright position, low-sodium diet)	4.2-19.8 ng/mL/hr or 4.2-19.8 mcg/L/hr
Adult (lying down, low-sodium diet)	0.4-3.2 ng/mL/hr or 0.4-3.2 mcg/L/hr

Many factors can affect renin test results. Dr. Houston will talk with you about any abnormal results that may be related to your symptoms and medical history.

High values

A high renin value can mean kidney disease, blockage of an artery leading to a kidney, Addison’s disease,cirrhosis, excessive bleeding (hemorrhage), or malignant high blood pressure is present.

Low values

A low renin value can mean Conn’s syndrome is present.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Eating natural black licorice in the 2 weeks before the test.
Taking some medicines used to treat high blood pressure.
Taking aspirin, caffeine, estrogens, or diuretics.
Your position (standing, sitting, or lying down) before the test is done or the time of day when the blood sample is drawn, as well as recent salt intake.
Taking very high doses of corticosteroids.
Being pregnant.

Sedimentation Rate

The sedimentation rate (sed rate) blood test measures how quickly red blood cells (erythrocytes) settle in a test tube in one hour. The more red cells that fall to the bottom of the test tube in one hour, the higher the sed rate.

When inflammation is present in the body, certain proteins cause red blood cells to stick together and fall more quickly than normal to the bottom of the tube. These proteins are produced by the liver and theimmune system under many abnormal conditions, such as an infection, an autoimmune disease, or cancer.

There are many possible causes of a high sedimentation rate. For this reason, a sed rate is done with other tests to confirm a diagnosis. After a diagnosis has been made, a sed rate can be done to help check on the disease or see how well treatment is working.

Why It Is Done

A sedimentation rate (sed rate) test is done to:

Find out if inflammation is present.
Check on the progress of a disease.
See how well a treatment is working.

Results

The sedimentation rate (sed rate) blood test measures how quickly red blood cells (erythrocytes) settle in a test tube.

Normal

Results are usually available right away.

Sedimentation rate
Men	0-15 millimeters per hour (mm/hr)
Women	0-20 mm/hr
Children	0-10 mm/hr
Newborns	0-2 mm/hr

High values

High sedimentation rates may be caused by:

Autoimmune diseases, such as systemic lupus erythematosus or rheumatoid arthritis.
Cancer, such as lymphoma or multiple myeloma.
Chronic kidney disease.
Infection, such as pneumonia, pelvic inflammatory disease, or appendicitis.
Inflammation of joints (such as polymyalgia rheumatica) and blood vessels (such as giant cell arteritis).
Inflammation of the thyroid gland (Graves’ disease).
Kidney, bone, joint, skin, or heart valve infections.
Pregnancy and preeclampsia (toxemia of pregnancy).
Viral infections.

Low values

Low values may be caused by:

High blood sugar levels.
Polycythemia.
Sickle cell disease.
Severe liver disease.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Pregnancy.
Anemia.
Having your menstrual period.
Age. Sed rates normally increase with age.
Medicines. Many medicines can change the results of this test. Be sure to tell Dr. Houston about all the nonprescription and prescription medicines you take.

Testosterone

A testosterone test checks the level of this male hormone (androgen) in the blood. Testosterone affects sexual features and development. In men, it is made in large amounts by the testicles. In both men and women, testosterone is made in small amounts by the adrenal glands; and, in women, by the ovaries.

The pituitary gland controls the level of testosterone in the body. When the testosterone level is low, the pituitary gland releases a hormone called luteinizing hormone (LH). This hormone tells the testicles to make more testosterone. See a picture of the pituitary gland .

Before puberty, the testosterone level in boys is normally low. Testosterone increases during puberty. This causes boys to develop a deeper voice, get bigger muscles, make sperm, and get facial and body hair. The level of testosterone is the highest around age 40, then gradually becomes less in older men.

In women, the ovaries account for half of the testosterone in the body. Women have a much smaller amount of testosterone in their bodies compared to men. But testosterone plays an important role throughout the body in both men and women. It affects the brain, bone and muscle mass, fat distribution, the vascular system, energy levels, genital tissues, and sexual functioning.

Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin (SHBG). Testosterone that is not bound (“free”) can also be checked if a man or a woman is having sexual problems.

Why It Is Done

A testosterone test is done to:

See why a man is having problems in fathering a child (infertility). A low amount of testosterone can lead to low sperm counts.
Check a man’s sexual problems. A low level of testosterone may lower a man’s sex drive or not allow him to have an erection (erectile dysfunction).
See whether a high level of testosterone is causing a boy younger than age 10 to have early signs of puberty.
Check a decreased sex drive in a woman. This may be due to the level of testosterone in her body.
Find out why a woman is developing male features, such as excessive facial and body hair (hirsutism) and a deep voice.
Find out why a woman is having irregular menstrual periods.
See if testosterone-lowering medicines are working in a man with advanced prostate cancer.
Find the cause of osteoporosis in a man.

Results

A testosterone test checks the level of this male hormone (androgen) in the blood.

Normal

Total testosterone
Men	270-1070 ng/dL (9-38 nmol/L)
Women	15-70 ng/dL (0.52-2.4 nmol/L)
Children	2-20 ng/dL or 0.07-0.7 nmol/L

The testosterone level for a postmenopausal woman is about half the normal level for a healthy, nonpregnant woman. And a pregnant woman will have 3 to 4 times the amount of testosterone compared to a healthy, nonpregnant woman.

Free testosterone
Men	50-210 pg/mL (174-729 pmol/L)
Women	1.0-8.5 pg/mL (3.5-29.5 pmol/L)

High values

In men, a high level of testosterone may be caused by cancer of the testicles or adrenal glands.
In boys younger than 10, a high level of testosterone may mean early (precocious) puberty, a tumor in the testicles, or an abnormal adrenal gland.
In women, a high level of testosterone may be caused by cancer of the ovaries or adrenal glands or bypolycystic ovary syndrome (PCOS).

Low values

In men or boys who have gone through puberty, a low level of testosterone may be caused by a problem with the testicles, such as slow development of, an injury to, or a lack of testicles. It can also be caused from treatment with the female hormone estrogen, a problem with the pituitary gland, or many long-term (chronic) illnesses.
A low testosterone level in men can also be caused by certain inherited diseases (such as Klinefelter syndrome or Down syndrome), liver disease (cirrhosis), or treatment for cancer of the prostate gland.
Chronic alcohol use can cause a low testosterone level.
In women, a low level of testosterone may be caused by an underactive pituitary gland, Addison’s disease, loss of ovary function through disease or surgery, and some medicines (such ascorticosteroids or estrogen).

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking medicines such as estrogen (including birth control pills), testosterone, corticosteroids, digoxin (Lanoxin), spironolactone (Aldactone), or barbiturates.
Having hyperthyroidism. This can raise sex hormone binding globulin (SHBG) levels. Hypothyroidismcan lower SHBG levels.
Taking medicines to treat prostate cancer.
Taking medicines that raise prolactin levels, such as certain seizure medicines.

Thyroid Hormone Tests

Thyroid hormone tests are blood tests that check how well the thyroid gland is working. The thyroid gland makes hormones that regulate the way the body uses energy.

The thyroid gland is a butterfly-shaped gland that lies in front of your windpipe (trachea), just below your voice box (larynx). The thyroid gland uses iodine from food to make two thyroid hormones: thyroxine (T4) and triiodothyronine (T3). The thyroid gland stores these thyroid hormones and releases them as they are needed.

Thyroid hormones are needed for normal development of the brain, especially during the first 3 years of life.Intellectual disability may occur if a baby’s thyroid gland does not produce enough thyroid hormone (congenital hypothyroidism). Older children also need thyroid hormones to grow and develop normally, and adults need the hormones to regulate the way the body uses energy (metabolism).

Thyroid hormone blood tests include:

Total thyroxine (T4). Most of the thyroxine (T4) in the blood is attached to a protein called thyroxine-binding globulin. Less than 1% of the T4 is unattached. A total T4 blood test measures both bound and free thyroxine. Free thyroxine affects tissue function in the body, but bound thyroxine does not.
Free thyroxine (FTI or FT4). Free thyroxine (T4) can be measured directly (FT4) or calculated as the free thyroxine index (FTI). The FTI tells how much free T4 is present compared to bound T4. The FTI can help tell if abnormal amounts of T4 are present because of abnormal amounts of thyroxine-binding globulin.
Triiodothyronine (T3). Most of the T3 in the blood is attached to thyroxine-binding globulin. Less than 1% of the T3 is unattached. A T3 blood test measures both bound and free triiodothyronine. T3 has a greater effect on the way the body uses energy than T4, even though T3 is normally present in smaller amounts than T4.

Why It Is Done

Thyroid hormone tests are done to:

Find out what is causing an abnormal thyroid-stimulating hormone (TSH) test. For more information, see the topic Thyroid-Stimulating Hormone (TSH). This is the most common reason for thyroid hormone tests.
Check how well treatment of thyroid disease is working. The total thyroxine (T4), free thyroxine (FT4), and free thyroxine index (FTI) values are often used to keep track of treatment for hyperthyroidism.
Screen newborns to find out if the thyroid gland function is normal. A condition called congenital hypothyroidism can prevent normal growth and development and cause other severe problems, such as intellectual disability, if it is not treated soon after birth.

Results

Thyroid hormone tests are blood tests that check how well the thyroid gland is working.

Normal

Results are usually available within a few days.

Labs generally measure free T4 (FT4) levels, but also may measure total thyroxine (T4) and T3 uptake (T3U). Results of these thyroid hormone tests may be compared to your thyroid-stimulating hormone (TSH)results.

Thyroid hormone tests
Total thyroxine (T4):	11.8-22.6 (mcg/dL) or 152-292 (nmol/L) in newborns up to 14 days old6.4-13.3 mcg/dL (83-172 nmol/L) in babies and older children5.4-11.5 mcg/dL (57-148 nmol/L) in adults
Free thyroxine (FT4):	0.7-2.0 ng/dL (ng/dL) or 10-26 (pmol/L)
Total triiodothyronine (T3):	32-250 ng/dL (0.49-3.85 nmol/L) in newborns up to 14 days old82-245 ng/dL (1.3-3.8 nmol/L) in babies and older children80-200 ng/dL (1.2-3.1 nmol/L) in adults
Free triiodothyronine (FT3):	260-480 pg/dL (4.0-7.4 pmol/L)
Free thyroxine index (FTI):	1.5-4.5 (index)

Many conditions can change thyroid hormone levels. Dr. Houston will talk with you about any abnormal results that may be related to your symptoms and past health.

High values

High thyroid hormone levels (hyperthyroidism) may be caused by:

Diseases of the thyroid gland, such as Graves’ disease, thyroiditis, or a goiter that contains one or more abnormal growths (nodules).
Taking too much thyroid medicine.

Low values

Low thyroid hormone levels (hypothyroidism) may be caused by:

Thyroid disease, such as thyroiditis.
Pituitary gland disease.
Destruction of the thyroid gland by surgery or radiation.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking certain medicines, such as:
- Corticosteroids, estrogen, progesterone, or birth control pills.
- Blood-thinning medicines such as aspirin, heparin, or warfarin (Coumadin).
- Antiseizure medicines such as Dilantin or Tegretol.
- Heart medicines such as amiodarone or propranolol.
- Lithium.
Having recently had an X-ray test that uses contrast material.
Being pregnant.

Total Serum Protein

A total serum protein test measures the total amount of protein in the blood. It also measures the amounts of two major groups of proteins in the blood: albumin and globulin.

Albumin is made mainly in the liver. It helps keep the blood from leaking out of blood vessels. Albumin also helps carry some medicines and other substances through the blood and is important for tissue growth and healing.
Globulin is made up of different proteins called alpha, beta, and gamma types. Some globulins are made by the liver, while others are made by the immune system. Certain globulins bind with hemoglobin. Other globulins transport metals, such as iron, in the blood and help fight infection. Serum globulin can be separated into several subgroups by serum protein electrophoresis
A test for total serum protein reports separate values for total protein, albumin, and globulin. The amounts of albumin and globulin also are compared (albumin/globulin ratio). Normally, there is a little more albumin than globulin and the ratio is greater than 1. A ratio less than 1 or much greater than 1 can give clues about problems in the body.

Why It Is Done

Albumin is tested to:

Check how well the liver and kidneys are working.
Find out if your diet contains enough protein.
Help determine the cause of swelling of the ankles (edema) or abdomen (ascites) or of fluid collection in the lungs that may cause shortness of breath (pulmonary edema).

Globulin is tested to:

Determine your chances of developing an infection.
See if you have a rare blood disease, such as multiple myeloma or macroglobulinemia

Results

A total serum protein test is a blood test that measures the amounts of total protein, albumin, and globulin in the blood. Results are usually available within 12 hours.

Normal

Total serum protein
Total protein:	6.0-8.0 (g/dL) or 60-80 (g/L)
Albumin:	3.8-5.0 g/dL or 38-50 g/L
Alpha-1 globulin:	0.1-0.3 g/dL or 1-3 g/L
Alpha-2 globulin:	0.6-1.0 g/dL or 6-10 g/L
Beta globulin:	0.7-1.4 g/dL or 7-14 g/L
Gamma globulin:	0.7-1.6 g/dL or 7-16 g/L
Albumin/globulin ratio:	Greater than 1.0

High values

High albumin levels may be caused by:

Severe dehydration.

High globulin levels may be caused by:

Diseases of the blood, such as multiple myeloma, Hodgkin’s lymphoma, leukemia, macroglobulinemia, or hemolytic anemia.
An autoimmune disease, such as rheumatoid arthritis, lupus, autoimmune hepatitis, or sarcoidosis.
Kidney disease.
Liver disease.
Tuberculosis.

Low values

Low albumin levels may be caused by:

A poor diet (malnutrition).
Severe burns.
Kidney disease.
Liver disease.
An autoimmune disease, such as systemic lupus erythematosus (SLE) or rheumatoid arthritis.
Gastrointestinal malabsorption syndromes, such as sprue or Crohn’s disease.
Hodgkin’s lymphoma.
Uncontrolled diabetes.
Hyperthyroidism.
Heart failure.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

Taking medicines, such as corticosteroids, estrogens, male sex hormones (called androgens), growth hormone, or insulin.
Injuries or infections.
Prolonged bed rest, such as during a hospital stay.
A long-term (chronic) illness, especially if the disease interferes with what you are able to eat or drink.
Being pregnant.

29 Nov Lab Testing

Blood Glucose

Blood Glucose Testing

Blood Urea Nitrogen (BUN)

Blood Urea Nitrogen

C-Reactive Protein (CRP)

C-Reactive Protein (CRP)

Calcium (Ca) in Blood

Calcium (Ca) in Blood

Catecholamines in Blood

Catecholamines in Blood

Chloride (Cl)

Chloride (Cl)

Cholesterol and Triglycerides Tests

Cholesterol and Triglycerides Tests

Complete Blood Count (CBC)

Complete Blood Count (CBC)

Cortisol in Blood

Cortisol in Blood

Creatinine and Creatinine Clearance

Creatinine and Creatinine Clearance

Dehydroepiandrosterone

Dehydroepiandrosterone

Estrogens

Estrogens

Follicle-Stimulating Hormone

Follicle-Stimulating Hormone

Glycohemoglobin (HbA1c, A1c)

Glycohemoglobin (HbA1c, A1c)

Homocysteine

Homocysteine

Liver Function Tests

Liver Function Tests

Luteinizing Hormone

Luteinizing Hormone

Magnesium (Mg)

Magnesium (Mg)

Microalbumin Urine Test

Microalbumin Urine Test

Phosphate in Blood

Phosphate in Blood

Potassium (K) in Blood

Potassium (K) in Blood

Prostate-Specific Antigen (PSA)

Prostate-Specific Antigen (PSA)

Renin Assay

Renin Assay

Sedimentation Rate

Sedimentation Rate

Testosterone

Testosterone

Thyroid Hormone Tests

Thyroid Hormone Tests

Total Serum Protein

Total Serum Protein

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