Indirect Bilirubin

Does this test have other names?

Unconjugated bilirubin

What is this test?

This test measures the amount of bilirubin in your blood. Your body makes bilirubin when it breaks down hemoglobin. Hemoglobin is a protein in red blood cells. The breakdown of hemoglobin is called hemolysis.

Your liver removes bilirubin from your body. So measuring bilirubin is one way to check how well your liver is working.

Why do I need this test?

You may need this test if the results of a total bilirubin blood test are abnormal.

Your total bilirubin may be tested if your healthcare provider suspects you have certain health conditions. These include transfusion reaction, Gilbert syndrome, Dubin-Johnson syndrome, Rotor syndrome, or Crigler-Najjar syndrome. It may also be done as part of routine blood testing to screen for liver problems or damage such as cirrhosis. Or it may be done to screen for a blood disease such as hemolytic anemia or pernicious anemia. You may also have bilirubin testing to track a disease you have or are being treated for.

What other tests might I have along with this test?

Your healthcare provider 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:

• Serum aminotransferases such as aspartate and alanine

• Alkaline phosphatase

• Albumin

• Prothrombin time. This is a clotting test.

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

Indirect and direct bilirubin make up your total bilirubin. When total bilirubin is abnormal, it is important to measure direct and indirect bilirubin levels. Bilirubin is measured in milligrams per deciliter (mg/dL). An example of normal values for adults is:

• Total bilirubin: 0.3 to 1.9 mg/dL

• Direct bilirubin: 0.0 to 0.3 mg/dL

Indirect bilirubin is the difference between total and direct bilirubin.

Common causes of higher indirect bilirubin include:

• Hemolytic anemia. This means your body is getting rid of too many red blood cells.

• Bleeding into the skin caused by injury

• Bleeding in the lung caused by a blood clot

• A gene problem that causes slightly higher indirect bilirubin levels without other signs or symptoms of disease

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Different things may affect bilirubin levels. Vigorous exercise can raise bilirubin levels. So can the HIV medicine atazanavir.

Caffeine can lower total bilirubin. So can certain medicines. These include:

• Barbiturates

• Penicillin

• High doses of salicylates

Men have slightly higher levels of bilirubin than women. African Americans also have slightly higher levels of bilirubin than people of other ethnic backgrounds.

How do I get ready for this test?

You may need to fast several hours before this test. Ask your healthcare provider how you should prepare for the test. Instructions can vary.

Several types of medicine may change the bilirubin level in your blood. Be sure your healthcare provider 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.