A bilirubin test checks liver health by measuring the levels of bilirubin in the blood. Bilirubin is a substance produced by the breakdown of red blood cells.

Bilirubin (bil-ih-ROO-bin) passes through the liver and is eventually excreted out of the body.

Higher than usual levels of bilirubin may mean different types of liver or bile duct problems. Sometimes, higher bilirubin levels may be caused by an increased rate of destruction of red blood cells.

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

• Find out why the skin and eyes are yellow, a condition known as jaundice. Jaundice is caused by high levels of bilirubin. This test is commonly used to measure bilirubin levels in newborns with infant jaundice.
• Check for a blockage in the bile ducts in the liver or the gallbladder.
• Look for liver disease, particularly hepatitis, or monitor disease progression.
• Check on anemia caused by the destruction of red blood cells.
• See how a treatment is working.
• Look for a suspected drug toxicity.

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

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

The blood sample for a bilirubin test is usually taken from a vein in the arm. The main risk associated with blood tests is soreness or bruising at the site of the blood draw. Most people don't have serious reactions to having blood drawn.

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 the 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. You also may experience some short-term discomfort at the site after the needle is removed. Blood for bilirubin testing in newborns is usually collected using a sharp lancet to break the skin of the heel. This is known as a heel stick. There may be slight bruising at the puncture site afterward.

Your blood goes to a laboratory for analysis. You can usually return to usual activities immediately.

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

Typical 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. Typical results for direct bilirubin are generally 0.3 mg/dL.

These results may vary slightly from laboratory to laboratory. Results may be slightly different for women and children. Results also may be affected by certain medicines. For this reason, be sure to tell your healthcare team about any medicines you take. Your care team may ask you to stop taking medicines before the test.

Lower than usual bilirubin levels are usually not a concern. Higher levels of direct bilirubin in your blood may mean your liver isn't clearing bilirubin properly. This may mean there is liver damage or disease. Higher levels of indirect bilirubin may be a sign of other problems.

One common cause of elevated bilirubin is Gilbert syndrome. Gilbert syndrome is a harmless liver condition in which the liver doesn't properly process bilirubin. A healthcare professional may order more tests to investigate your condition. Bilirubin test results also may be used to monitor certain conditions, such as jaundice.