The D-xylose absorption test measures the level of D-xylose, a type of sugar, in a blood or urine sample. This test is done to help diagnose problems that prevent the small intestine from absorbing nutrients in food. D-xylose is normally easily...

An ammonia test measures the amount of ammonia in the blood. Most ammonia in the body forms when protein is broken down by bacteria in the intestines. The liver normally converts ammonia into urea, which is then eliminated in urine. Ammonia levels in the blood rise when the liver is not able to convert ammonia to urea...

An amylase test measures the amount of this enzyme in a sample of blood taken from a vein or in a sample of urine. Normally, only low levels of amylase are found in the blood or urine. But if the pancreas or salivary glands become damaged or blocked, more amylase is usually released into the blood and urine. In the...

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...

Catecholamines (say "kat-uh-KOH-luh-meens") are hormones made mostly by your adrenal glands as a reaction to stress. When you feel stressed, these hormones increase heart rate, blood pressure, breathing rate, muscle strength, and mental alertness. They also lower the amount of blood that goes to the skin and intestines...

Partial thromboplastin time (PTT) is a blood test that measures the time it takes your blood to clot. A PTT test can be used to check for bleeding problems. Blood clotting factors are needed for blood to clot (coagulation). The partial thromboplastin time is an important test because the time it takes your blood to clot...

Fetal fibronectin is a protein that helps keep the amniotic sac attached to the wall of the uterus during pregnancy. If there is a problem with the amniotic sac staying attached to the uterus, high amounts of fetal fibronectin can end up in the vaginal fluid. This can mean there is an increased chance of having a...

A creatine kinase (CK) test checks the level of the enzyme creatine kinase, which is found in heart tissue and skeletal muscles. This enzyme also can be found in smaller amounts in the brain. A blood test to check the level of CK can show if there has been damage to the heart, skeletal muscles, brain, and sometimes...

An aldosterone test measures the level of aldosterone (a hormone made by the adrenal glands) in the urine. Aldosterone helps regulate sodium and potassium levels in the body. This helps control blood pressure and the balance of fluids and electrolytes in the blood. The kidney hormone renin normally stimulates the...

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)...

DHEA-S (dehydroepiandrosterone sulfate) is a male hormone (androgen) that is made in the adrenal glands. The body turns it into testosterone. A test for DHEA-S checks the level of this hormone in the blood. Testosterone affects sexual features and development. In men, it is made in large amounts by the testicles. In...

A cortisol test measures the level of the hormone cortisol in a 24-hour sample of urine. The cortisol level may show problems with the adrenal glands or the pituitary gland. Cortisol is made by the adrenal glands. Cortisol levels get higher when the pituitary gland releases adrenocorticotropic hormone (ACTH). Cortisol...

A growth hormone (GH) test measures the amount of human growth hormone (GH) in the blood. GH is made by the pituitary gland and is needed for growth. It plays an important role in how the body uses food for energy ( metabolism). The amount of GH in the blood changes during the day and is affected by exercise, sleep...

A renin assay blood test is done to find the cause of high blood pressure (hypertension). Renin is an enzyme made 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...

A vitamin D test measures the amount of vitamin D in the blood. The vitamin D test is also called the 25-hydroxy vitamin D, or 25(OH)D, test. Your body needs vitamin D to absorb calcium. Calcium keeps your bones and muscles healthy and strong. If your muscles don't get enough calcium, they can cramp, hurt, or feel weak...

A bilirubin test measures the amount of bilirubin in a blood sample. Bilirubin is a brownish yellow substance found in bile. It is produced when the liver breaks down old red blood cells. Bilirubin is then removed from the body through the stool (feces) and gives stool its normal color. Bilirubin circulates in the...

The high-sensitivity C-reactive protein (hs-CRP) test is a blood test that finds lower levels of C-reactive protein (CRP). This protein measures general levels of inflammation in your body. The hs-CRP can be used to find the risk for heart disease and stroke in people who don't already have heart disease. The hs-CRP...

Discusses serum osmolality test used to check for dehydration, certain poisons, cause of seizures, and other problems. Covers how it is done and how to prepare for it. Also covers what test results may mean.

A lactic acid test is a blood test that measures the level of lactic acid made in the body. Most of it is made by muscle tissue and red blood cells. When the oxygen level in the body is normal, carbohydrate breaks down into water and carbon dioxide. When the oxygen level is low, carbohydrate breaks down for energy and...

A vitamin B12 test measures the amount of vitamin B12 in the blood. The body needs this B vitamin to make blood cells and to maintain a healthy nervous system. Vitamin B12 is found in animal products such as meat, shellfish, milk, cheese, and eggs. Most people who eat animal products are not likely to develop vitamin...

Laparoscopy (say "lap-uh-ROSS-kuh-pee") is a type of surgery that uses very small cuts. These cuts are called incisions. The doctor puts a lighted tube through incisions in your belly. This tube is called a scope. Then the doctor puts special tools through the tube to do the surgery. The surgery may be done to diagnose...

Explains why and how a test is done for galactosemia, a rare disease passed from parents to children. Covers blood or urine test that checks a newborn for enzymes needed to change galactose from milk into glucose.

A lipase test measures the amount of this enzyme in a blood sample. High amounts of lipase may be found in the blood when the pancreas is damaged or when the tube leading from the pancreas (pancreatic duct) to the beginning of the small intestine is blocked.

Prealbumin is a protein that is made in the liver and released in the blood. It helps carry certain hormones that regulate the way the body uses energy and other substances through the blood.

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...