An aldosterone test measures the level of aldosterone (a hormone made by the adrenal glands), in the blood. 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 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...

A sodium test checks how much sodium is in the blood. Sodium is both an electrolyte and mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Sodium is also important in how nerves and muscles work. Most of the sodium in the body is found in blood...

During the first trimester of pregnancy, screening tests for birth defects may be done. These tests look for possible problems with your baby. The tests may be called first-trimester screening, combined first-trimester screening, or the combined screening. The screening tests show the chance of your baby having certain...

Hemochromatosis gene (HFE) testing is a blood test used to check for hereditary hemochromatosis, an inherited disorder that causes the body to absorb too much iron. The iron then builds up in the blood, liver, heart, pancreas, joints, skin, and other organs. In its early stages, hemochromatosis can cause joint and belly...

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...

Lab tests play an important role in your health care. They help your doctor make a diagnosis or treatment decisions. But they may not provide all of the information that your doctor needs. Your doctor will not usually make a decision or diagnosis based only on the results of a lab test, unless the test results are...

A carbon monoxide blood test is used to detect carbon monoxide poisoning. Poisoning can happen if you breathe air that contains too much carbon monoxide (CO). This gas has no color, odor, or taste, so you can't tell when you are breathing it. The test measures the amount of hemoglobin in your blood that has bonded with...

Has links on complete blood count, sedimentation rate tests, and anemia. Also includes links to lymph topics such as swollen glands/other lumps under the skin and lymphedema.

A toxicology test ("tox screen") checks for drugs or other chemicals in your blood, urine, or saliva. Drugs can be swallowed, inhaled, injected, or absorbed through the skin or a mucous membrane. In rare cases, a tox screen may check your stomach contents or sweat. A tox screen may check for one certain drug or for up...

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 formed when food is changed into energy through a process called...

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...

A ketone test checks for ketones in your blood or urine. Ketones are substances that are made when the body breaks down fat for energy. Normally, your body gets the energy it needs from carbohydrate in your diet. But stored fat is broken down and ketones are made if your diet does not contain enough carbohydrates to...

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...

Syphilis tests are done to check for a syphilis infection. They look for antibodies to the bacteria that cause syphilis. Some tests look for the syphilis bacteria. Syphilis is a sexually transmitted infection. That means it is spread through sexual contact: vaginal, anal, or oral sex. It can also spread to the fetus of...

A prolactin test measures the level of the hormone prolactin, which is made by the pituitary gland, in your blood. Pregnant women have high levels of prolactin, which helps make breast milk. During pregnancy, prolactin levels increase by 10 to 20 times. After the baby is born, prolactin stays high if you are...

Helicobacter pylori tests are used to detect a Helicobacter pylori ( H. pylori) infection in the stomach and upper part of the small intestine ( duodenum). H. pylori can cause peptic ulcers. But most people with H. pylori in their digestive systems do not develop ulcers. Four tests are used to detect H. pylori: 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...

Guides you through choosing a test to check for colorectal cancer. Looks at symptoms of colorectal cancer. Covers stool tests, sigmoidoscopy, colonoscopy, and virtual colonoscopy. Includes interactive tool to help you make your decision.

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)...

What is Rh sensitization during pregnancy? You may have Rh-negative blood, and your baby may have Rh-positive blood. If the two types of blood mix, your body will make antibodies. This is called Rh sensitization. In most cases, this isn't a problem the first time you're pregnant. But in future pregnancies, sensitization...

Describes monitoring blood sugar levels in those with diabetes. Gives step-by-step instructions. Covers how to record testing results and how to prevent sore fingers.

Covers blood test that checks the amount of sugar (glucose) bound to hemoglobin. Explains that test is done to check how well you are managing your diabetes. Covers how it is done and discusses results.