This test measures the amount of bilirubin in your blood. Your body produces bilirubin when it breaks down hemoglobin, a protein in red blood cells. This breakdown is called hemolysis.
Your liver removes bilirubin from your body, so measuring it is one way to check how well your liver is working.
You may need this test if the results of a total bilirubin blood test are abnormal. When total bilirubin is abnormal, it is important to measure direct and indirect bilirubin levels.
Your total bilirubin may be tested if your doctor suspects you have certain medical conditions. It may also be done as part of routine blood testing to screen for liver problems or a blood disease called hemolytic anemia. You may also have bilirubin testing to track a disease you have or are being treated for.
An increase in direct bilirubin is most likely caused by a blockage in the liver. An increase in indirect bilirubin is most likely caused by destruction of too many red blood cells.
Your doctor may order many other tests along with direct, indirect, and total bilirubin that assess your liver health. These tests are called liver function tests and may include:
Prothrombin time (a clotting test)
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Bilirubin travels through your body in two ways. Bilirubin that is attached to a protein is called indirect or unconjugated bilirubin. Bilirubin that moves freely in the blood is called direct or conjugated bilirubin. Together they make up your total bilirubin.
Bilirubin is measured in milligrams per deciliter (mg/dL). Normal values for adults are:
Total bilirubin: 0.3 to 1.0 mg/dLDirect bilirubin: 0.0 to 0.2 mg/dL
Indirect bilirubin is the difference between total and direct bilirubin.
Common causes of elevated indirect bilirubin include:
Hemolytic anemia, or destruction of too many red blood cells
Bleeding into the skin caused by injury
Bleeding in the lung caused by a blood clot
A genetic abnormality that causes slightly increased indirect bilirubin levels without other signs or symptoms of disease. This affects about 5 percent of the population.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Different factors may affect bilirubin levels. These include:
Recent X-ray tests that used a contrast dye
Foods like yams and carrots as well as a high-fat meal
Some drugs and nicotinic acid (vitamin B3)
Excessive fasting and anorexia, an eating disorder
Recent sun or artificial light exposure that lasts for an hour or more
You may need to fast before this test. Ask your doctor how you should prepare. In addition, be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.