Bilirubin test

Bilirubin testing checks for levels of bilirubin in your blood. Bilirubin (bil-ih-ROO-bin), an orange-yellow pigment, is a waste product of the normal breakdown of red blood cells. Bilirubin passes through the liver and eventually out of the body — mostly in feces, a small amount in urine.

Before reaching the liver, bilirubin is called unconjugated, meaning uncombined. In the liver, bilirubin combines with certain sugars to create a water-soluble form called conjugated bilirubin. Conjugated bilirubin passes out of the liver, and in the colon, it is converted back into the unconjugated form en route to being excreted from the body.

Most laboratories use a test that detects conjugated bilirubin, which is called direct. By subtracting the direct bilirubin from the amount of total bilirubin, an estimate of unconjugated bilirubin, called indirect, is obtained.

Higher than normal levels of direct or indirect bilirubin may indicate different types of liver problems. Occasionally, higher bilirubin levels may indicate an increased rate of destruction of red blood cells (hemolysis).


Why it's done Risks What you can expect Results

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

  • Investigate jaundice — elevated levels of bilirubin can cause yellowing of your skin and the whites of your eyes (jaundice). The most common use of the test is to measure bilirubin levels in newborns.
  • Determine whether there's a blockage in your liver's bile ducts
  • Help detect or monitor the progression of other liver disease, such as hepatitis
  • Help detect increased destruction of red blood cells
  • Help follow how a treatment is working
  • Help evaluate suspected drug toxicity

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

  • Liver function tests. A group of 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.
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