Creatinine and creatinine clearance tests measure the level of the waste product creatinine (say "kree-AT-uh-neen") in your blood and urine. These tests tell how well your kidneys are working. Another substance, creatine (say "KREE-uh-teen"), is...

Discusses blood test to check the different types of hemoglobin in the blood. Covers how some diseases, such as sickle cell disease, aplastic anemia, and leukemia, have abnormal types of hemoglobin. Discusses possible test results.

A sweat test, also called a sweat chloride test, measures the amount of chloride in sweat. It is done to help diagnose cystic fibrosis. Normally, sweat on the skin surface contains very little chloride. People with cystic fibrosis have a high level...

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. LH helps regulate the menstrual cycle and egg production ( ovulation). LH levels normally change with the phase of the menstrual cycle. This hormone goes up fast just before...

Covers why and how parathyroid hormone tests are done. Covers what possible results might mean. Includes info on what might affect the test.

Vision is the result of electrical signals that travel between the retina and the part of the brain involved with vision (occipital cortex). Electrophysiology tests check to see how well this visual nerve pathway sends the electrical signals needed for vision. These tests measure electrical activity that occurs in your...

Cardiac enzyme studies measure the levels of enzymes and proteins that are linked with injury of the heart muscle. The test checks for the proteins troponin I (TnI) and troponin T (TnT). If your heart muscle is injured, such as from a heart attack, troponin proteins leak out of damaged heart muscle cells, and their...

A gastrin test measures the level of the hormone gastrin in the blood. Gastrin is produced by cells, called G cells, in the stomach lining. When food enters the stomach, G cells trigger the release of gastrin in the blood. As blood levels of gastrin rise, the stomach releases acid (gastric acid) that helps break down...

The carcinoembryonic antigen (CEA) test measures the amount of this protein that may appear in the blood of some people who have certain kinds of cancers, especially cancer of the large intestine ( colon and rectal cancer). It may also be present in people with cancer of the pancreas, breast, ovary, or lung. CEA is...

An estrogen test measures the level of the most important estrogen hormones in a blood or urine sample. It measures estradiol, estriol, and estrone. Estradiol is the most common type of estrogen measured for nonpregnant women. The amount of estradiol in a woman's blood varies throughout her menstrual cycle. After...

Doctors are experts on medical care. But you are the expert on yourself and your life. That's why it's important to be an active patient. When you're actively involved in decisions about your care, you can be sure that your choices reflect your values and beliefs. Here are some ways to become more active and involved in...

An adrenocorticotropic hormone test measures the level of adrenocorticotropic hormone (ACTH) in the blood to check for problems with the pituitary gland and adrenal glands. ACTH is made in the pituitary gland in response to the release of another hormone, called corticotropin-releasing hormone (CRH), by the...

Discusses toxoplasmosis test, a blood test that checks pregnant women for antibodies to the Toxoplasma gondii parasite. Covers why and how it is done. Also discusses what results mean.

A rheumatoid factor (RF) blood test measures the amount of the RF antibody present in the blood. Normally, antibodies are produced by the immune system to help destroy and get rid of invading bacteria and viruses that can cause disease. But the RF...

The overnight dexamethasone suppression test checks to see how taking a steroid medicine called dexamethasone changes the levels of the hormone cortisol in the blood. This test checks for a condition in which large amounts of cortisol are produced by the adrenal glands ( Cushing's syndrome). Normally, when the pituitary...

The serum protein electrophoresis (SPEP) test measures specific proteins in the blood to help identify some diseases. Proteins are substances made up of smaller building blocks called amino acids. Proteins carry a positive or a negative electrical charge, and they move in fluid when placed in an electrical field. Serum...

An antinuclear antibody (ANA) test measures the amount and pattern of antibodies in your blood that work against your own body (autoimmune reaction). The body's immune system normally attacks and destroys foreign substances such as bacteria and viruses. But in disorders known as autoimmune diseases, the immune system...

Provides overview of tests used to find out what a person might be allergic to. Covers skin and blood tests. Explains why and how each test is done. Discusses risks. Explains results and offers points to consider before having tests.

Describes various sleep studies used to diagnose sleep disorders. Discusses problems like snoring, sleep apnea, insomnia, and narcolepsy. Covers common sleep studies, including polysomnograms, multiple sleep latency tests, and the maintenance of wakefulness test.

What is chronic myeloid leukemia (CML)? Chronic myeloid leukemia (CML) is type of cancer in which the bone marrow makes too many white blood cells. In CML, young white blood cells grow abnormally, and they don't mature or die off as they should. These abnormal cells can crowd out normal blood cells and cause problems...

Use this form for any tests your doctor recommends, such as blood tests, urine tests, or X-rays. General questions What is the name of the test? Why do I need this test? What might happen if the test is delayed or not done? How accurate is the test? Are there other tests that are more accurate? How much does the test...

Has info on finger, hand, and wrist problems as well as shoulder injuries. Also has info on osteoarthritis and fibromyalgia with links to low back pain exercises and info on tennis elbow surgery.

Education on type 1 diabetes, type 2 diabetes, and gestational diabetes. Includes info on juvenile diabetes and prediabetes. Discusses symptoms and treatment. Also looks at how to manage blood sugar levels, diet, and medicines, including insulin.

Looks at infertility. Includes info on various tests used to find out why someone can't get pregnant. Covers treatments, including medicine to help stimulate ovulation and procedures to increase sperm count.

What is teen substance use? Many teens try substances like alcohol or drugs. Some try them only a few times and stop. Teens who keep using substances may form a strong need for them. This can lead to substance use disorder. Substances teens may try include tobacco, alcohol, marijuana or other drugs, household products...