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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, 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 produce 250 to 350 milligrams (mg) of bilirubin each day.

Bilirubin that is bound to a certain protein is called unconjugated, or indirect, bilirubin. Conjugated, or direct, bilirubin travels freely through your bloodstream to your liver. Most of this bilirubin passes into the small intestine, but 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

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 doctor suspects that you may have:

  • Hepatitis. Your liver can become inflamed for different reasons, including excessive 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, resulting in 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 doctor 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 doctor may order blood tests for these enzymes, such as:

  • Alkaline phosphatase, or ALP

  • Aspartate transaminase, or AST

  • Alanine transaminase, or ALT

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

What do my test results mean?

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.

Results are given in milligrams per deciliter (mg/dL). Normal results of the blood test range from 0 to 0.1 mg/dL in adults.

If your results on the blood test are higher, bilirubin may also show up in your urine. Urine in adults normally contains only 0.02 mg/dL. Most urine tests will not detect this amount.

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

  • Certain inherited diseases

How is this test done?

The test requires either a blood sample, which is drawn through a needle from a vein in your arm, or a urine sample.

Does this test pose any risks?

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.

What might affect my test results?

Strenuous exercise and pregnancy can affect your results. Vitamin C, androgen hormones, and certain drugs, including phenazopyridine (Pyridium) 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.  But 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.