A bilirubin test measures the levels of bilirubin in your blood. Bilirubin (bil-ih-ROO-bin) is a yellowish pigment that is made during the normal breakdown of red blood cells. Bilirubin passes through the liver and is eventually excreted out of the body.

Higher than normal levels of bilirubin may indicate different types of liver or bile duct problems. Occasionally, higher bilirubin levels may be caused by an increased rate of destruction of red blood cells (hemolysis).

Bilirubin testing is usually done as part of a group of tests to check the health of your liver. Bilirubin testing may be done to:

• Investigate jaundice — a yellowing of the skin and eyes caused by elevated levels of bilirubin. A common use of this test is to measure bilirubin levels in newborns to check for infant jaundice.
• Determine whether there might be blockage in your bile ducts, in either the liver or the gallbladder.
• Help detect liver disease, particularly hepatitis, or monitor its progression.
• Help evaluate anemia caused by the destruction of red blood cells.
• Help follow how a treatment is working.
• Help evaluate a suspected drug toxicity.

Some common tests that might be done at the same time as bilirubin testing include

• Liver function tests. Blood tests that measure certain enzymes or proteins in your blood.
• Albumin and total protein. Levels of albumin — a protein made by the liver — and total protein show how well your liver is making proteins that your body needs to fight infections and perform other functions.
• Complete blood count. This test measures several components and features of your blood.
• Prothrombin time. This test measures the clotting time of plasma.

Bilirubin testing is done using a blood sample. Usually, the blood is drawn through a small needle inserted into a vein in the bend of your arm. A small tube is attached to the needle to collect the blood.

You may feel a quick pain as the needle is inserted into your arm and experience some short-term discomfort at the site after the needle is removed. Blood for bilirubin testing in newborns is usually obtained using a sharp lancet to break the skin of the heel (heel stick). There may be slight bruising at the puncture site afterward.

Your blood will be sent to a laboratory for analysis. You can usually return to normal activities immediately.

Bilirubin test results are expressed as direct, indirect or total bilirubin. Total bilirubin is a combination of direct and indirect bilirubin. Typically, you'll get results for direct and total bilirubin.

Normal results for a total bilirubin test are 1.2 milligrams per deciliter (mg/dL) for adults and usually 1 mg/dL for those under 18. Normal results for direct bilirubin are generally 0.3 mg/dL.

These results may vary slightly from laboratory to laboratory. Normal results may be slightly different for women and children, and results may be affected by certain foods, medications or strenuous exercise. Be sure to tell your doctor about any foods or medications you've taken and your activity levels so that your results can be interpreted correctly.

Lower than normal bilirubin levels are usually not a concern. Elevated levels may indicate liver damage or disease.

Higher than normal levels of direct bilirubin in your blood may indicate your liver isn't clearing bilirubin properly. Elevated levels of indirect bilirubin may indicate other problems.

One common, and harmless, cause of elevated bilirubin is Gilbert's syndrome, a deficiency in an enzyme that helps break down bilirubin. Your doctor may order further tests to investigate your condition. Bilirubin test results also may be used to monitor the progression of certain conditions, such as jaundice.