Bilirubin is a yellowish pigment found in bile, a fluid made by the liver.
This article discusses the laboratory test that is done to measure bilirubin in the blood.
A small amount of older red blood cells are replaced by new blood cells every day. Bilirubin is left after these older blood cells are removed. The liver helps break down bilirubin so that it can be removed from the body in the stool.
Bilirubin may also be measured with a urine test.
Total bilirubin - blood; Unconjugated bilirubin - blood; Indirect bilirubin - blood; Conjugated bilirubin - blood; Direct bilirubin - blood
How the test is performed
A blood sample is needed. This may be taken from a vein. The test is called a venipuncture.
How to prepare for the test
You should not eat or drink for at least 4 hours before the test. Your health care provider may instruct you to stop taking drugs that affect the test.
Many drugs may change the bilirubin levels in your blood. Make sure your doctor knows which medications you are taking.
Why the test is performed
Large amounts of bilirubin in the blood can lead to jaundice. Jaundice is a yellow color in the skin, mucus membranes, or eyes.
Jaundice is the most common reason to check bilirubin levels.
- Most newborns have some jaundice. The doctor or nurse will often check the newborn's bilirubin level.
- The test may also be done in older infants, children, and adults who develop jaundice.
A bilirubin test will also be done if your doctor thinks you may have liver or gallbladder problems.
It is normal to have some bilirubin in your blood. Normal levels are:
- Direct (also called conjugated) bilirubin: 0 to 0.3 mg/dL
- Total bilirubin: 0.3 to 1.9 mg/dL
Note: mg/dL = milligrams per deciliter
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common results for these tests. Some laboratories use different measurements or may test different samples.
What abnormal results mean
In newborns, bilirubin levels are higher for the first few days of life. Your child's doctor must consider the following when deciding whether your baby's bilirubin levels are too high:
- How fast the level has been rising
- Whether the baby was born early
- How old the baby is
Jaundice can also occur when more red blood cells than normal are broken down. This can be caused by:
- Erythroblastosis fetalis
- Hemolytic anemia
- Transfusion reaction
The following liver problems may also cause jaundice or high bilirubin levels:
- Cirrhosis (scarring of the liver)
- Liver disease
- Gilbert's disease
The following problems with gallbladder or bile ducts may cause higher bilirubin levels:
- Biliary stricture
- Cancer of the pancreas or gallbladder
Berk PD, Korenblat KM. Approach to the patient with jaundice or abnormal liver test results. In: Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 149.
Pratt DS. Liver chemistry and function tests. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier;2010:chap 73.