Direct Bilirubin

Does this test have other names?

Conjugated bilirubin

What is this test?

This test looks for bilirubin in your blood or urine.

Bilirubin is a substance made when your body breaks down old red blood cells. This is a normal process. Bilirubin is also part of bile, which your liver makes to help digest the food you eat.

A small amount of bilirubin in your blood is normal. Healthy adults make 250 to 350 milligrams (mg) of bilirubin each day.

Bilirubin that is bound to a certain protein (albumin) in the blood is called unconjugated, or indirect, bilirubin. Conjugated, or direct, bilirubin travels from the liver into the small intestine. A very small amount passes into your kidneys and is excreted in your urine. This bilirubin also gives urine its distinctive yellow color.

This test is usually done to look for liver problems, such as hepatitis, or blockages, such as gallstones.

Why do I need this test?

You may need this test if your liver doesn't seem to be working the way it should. Signs and symptoms include:

• Jaundice, or yellowing of your skin and whites of your eyes

• Dark-colored urine

• Nausea

• Vomiting

• Fatigue

• Pain or swelling in the belly

You may also have this test if you drink a lot of alcohol on a regular basis. Drinking too much alcohol can damage the liver over time, so you may have this test to check for signs of possible liver damage.

You may also need this test if your healthcare provider suspects that you may have:

• Hepatitis. Your liver can become inflamed for different reasons, including excessive drug or alcohol use and infection from hepatitis viruses. Inflammation of the liver is called hepatitis. When liver cells are damaged from hepatitis, the liver may release both indirect and direct bilirubin into the bloodstream. This causes higher levels.

• Gallstones. The bile duct is a tube that carries bile to the small intestine. Bilirubin or cholesterol can form stones that block the duct. This causes bilirubin—mostly direct bilirubin—to rise in your bloodstream.

• Inflammation of the bile duct. Higher levels of direct bilirubin in your bloodstream may stem from inflammation in the tube that carries bile to the small intestine.

What other tests might I have along with this test?

Your healthcare provider is likely to order this test as part of a liver panel, or group of related liver tests. When your liver is damaged, liver enzymes may leak into your blood. Your provider may order blood tests for these enzymes, such as:

• Alkaline phosphatase, or ALP

• Aspartate transaminase, or AST

• Alanine transaminase, or ALT

Your healthcare provider may also order a test to check the levels of liver proteins like albumin.

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. 

Results are given in milligrams per deciliter (mg/dL). Normal results of the blood test range from 0 to 0.3 mg/dL in adults.

If your results on the blood test are higher, bilirubin may also show up in your urine. Bilirubin is not present in the urine of normal, healthy individuals. 

Results that are higher may mean that you have a liver problem, hepatitis, or gallstones.

Higher levels may also mean that you have:

• Septicemia, an infection in the bloodstream commonly known as blood poisoning

• Sickle cell anemia

• Certain cancers or tumors

• Certain rare inherited diseases

• Scarring of the bile ducts

If your results show low levels of bilirubin, your healthcare provider usually will not monitor them.

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. Or it is done with a urine sample. 

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?

Strenuous exercise and pregnancy can affect your results. Vitamin C, androgen hormones, and certain medicines, such as phenazopyridine and rifampin, can affect your results.

Taking all of your nutrition intravenously can also affect your results.

How do I get ready for this test?

You don't need to prepare for this test. 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.