Bilirubin testing checks for levels of bilirubin — an orange-yellow pigment — in your blood. Bilirubin results from the normal breakdown of red blood cells. As a normal process, bilirubin is carried in the blood and passes through your liver. Too much bilirubin may indicate liver damage or disease.
Before reaching your liver, as a break-down product of your red blood cells, the bilirubin is called indirect (unconjugated) bilirubin. Once in your liver, most bilirubin attaches to certain sugars creating what’s called direct (conjugated) bilirubin. Direct bilirubin is released into bile and stored in your gallbladder before eventually being excreted in your stool. Higher than normal levels of direct or indirect bilirubin may indicate different types of liver problems.
Bilirubin testing may be used for a variety of reasons and is usually done as part of a group of other tests that evaluate the health of your liver. Bilirubin testing may be done to:
- Investigate jaundice — elevated levels of bilirubin can cause yellowing of the whites of your eyes and yellowing of your skin (jaundice)
- Evaluate you if you’ve been exposed to hepatitis virus
- Determine whether there’s a blockage in your liver bile ducts
Bilirubin testing can also:
- Help detect or monitor the progression of other liver disease
- Help follow how a treatment is working
Some common liver tests that might be done at the same time as bilirubin testing include:
- Alanine transaminase (ALT). An enzyme found mainly in liver cells, ALT helps your body metabolize protein. Normally, ALT levels in the blood are low. When the liver is damaged, ALT is released in the bloodstream, raising the ALT levels in your blood.
- Aspartate transaminase (AST). The enzyme AST plays a role in the metabolism of alanine, an amino acid. AST is found in high concentrations in liver cells. An increase in AST levels may indicate liver damage or disease.
- Alkaline phosphatase (ALP). ALP is an enzyme found in high concentrations in the liver and bile ducts, as well as some other tissues. Higher than normal levels of ALP may indicate liver damage or disease.
- 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. Lower than normal levels may indicate liver damage or disease.
Additional tests that may be used to evaluate the liver include:
- Gamma-glutamyltransferase (GGT). This test measures the amount of the enzyme GGT in the blood. Higher than normal levels may indicate liver or bile duct damage.
- Lactate dehydrogenase (LDH). LDH is an enzyme found in many body tissues, including the liver. Elevated levels of LDH may indicate liver damage.
- Prothrombin time (PT). This test measures the clotting time of plasma. Increased PT may indicate liver damage.
During the test
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. You’ll be asked to roll up your shirt sleeve if you’re wearing long sleeves. The person drawing the blood might tie a band around your upper arm and ask you to make a fist. This causes your vein to stick out more, making it easier to insert the needle. The needle is attached to a small tube, in which your blood is collected. All of this usually takes just a few minutes.
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.
After the test
Once the needle is removed, you’ll be given a piece of gauze and a bandage to cover the area where the needle was inserted. You’ll be asked to gently apply pressure to the area for a minute or so, to help stop any bleeding.
Your blood will be sent to a laboratory for analysis. If the laboratory analysis is done on site, you could have your test results within hours. If your doctor sends your blood to an off-site laboratory, you may receive the results within several days.
Normal results for a typical bilirubin test are 0.1 to 1 milligram per deciliter (mg/dL) of total bilirubin (direct plus indirect) and 0 to 0.3 mg/dL for direct. Indirect bilirubin is usually measured by subtracting direct bilirubin from total bilirubin. These results may vary slightly from laboratory to laboratory but are typical for adult men. 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, for example, because of a blocked bile duct. Elevated levels of indirect bilirubin may indicate other problems, such as a deficiency in an enzyme that helps break down bilirubin (Gilbert syndrome). Your doctor may order further tests, such as ultrasound or additional blood tests, to further investigate your condition. Bilirubin test results also may be used to monitor the progression of certain conditions such as jaundice.