Bilirubin

Test Overview

A bilirubin test measures the amount of bilirubin in a blood sample. Bilirubin is a brownish yellow substance found in bile. It is produced when the liver breaks down old red blood cells. Bilirubin is then removed from the body through the stool (feces) and gives stool its normal brown color.

Bilirubin circulates in the bloodstream in two forms:

  • Indirect (or unconjugated) bilirubin. This form of bilirubin does not dissolve in water (it is insoluble). Indirect bilirubin travels through the bloodstream to the liver, where it is changed into a soluble form (direct or conjugated).
  • Direct (or conjugated) bilirubin. Direct bilirubin dissolves in water (it is soluble) and is made by the liver from indirect bilirubin.

Total bilirubin and direct bilirubin levels are measured directly in the blood, whereas indirect bilirubin levels are derived from the total and direct bilirubin measurements.

When bilirubin levels are high, the skin and whites of the eyes may appear yellow (jaundice). Jaundice may be caused by liver disease (hepatitis), blood disorders (hemolytic anemia), or blockage of the tubes (bile ducts) that allow bile to pass from the liver to the small intestine.

Too much bilirubin (hyperbilirubinemia) in a newborn baby can cause brain damage (kernicterus), hearing loss, problems with the muscles that move the eye, physical abnormalities, and even death. Therefore, some babies who develop jaundice may be treated with special lights (phototherapy) or a blood transfusion to lower their bilirubin levels.

In a newborn baby, the blood sample is usually taken from the heel (heel stick).

Why It Is Done

The bilirubin test is used to:

  • Check liver function and watch for signs of liver disease, such as hepatitis or cirrhosis, or the effects of medicines that can damage the liver.
  • Find out if something is blocking the bile ducts. This may occur if gallstones, tumors of the pancreas, or other conditions are present.
  • Diagnose conditions that cause increased destruction of red blood cells, such as hemolytic anemia or hemolytic disease of the newborn.
  • Help make decisions about whether newborn babies with neonatal jaundice need treatment. These babies may need treatment with special lights, called phototherapy. In rare cases, blood transfusions may be needed.

How To Prepare

Adults should not eat or drink for 4 hours before a bilirubin test.

No special preparation is needed for children before having a bilirubin test.

Tell your doctor if you:

  • Are taking any medicines.
  • Are allergic to any medicines.
  • Have had bleeding problems or take blood-thinners, such as aspirin or warfarin (Coumadin).
  • Are or might be pregnant.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?) .

How It Is Done

Blood sample from a heel stick

For a heel stick blood sample, several drops of blood are collected from the heel of your baby. The skin of the heel is first cleaned with alcohol and then punctured with a small sterile lancet. Several drops of blood are collected in a small tube. When enough blood has been collected, a gauze pad or cotton ball is placed over the puncture site. Pressure is maintained on the puncture site briefly, and then a small bandage is usually applied.

Instead of the standard heel stick, some hospitals may use a device called a transcutaneous bilirubin meter to check a newborn's bilirubin level. This small handheld device measures bilirubin levels when it is placed gently against the skin. With this device, there may be no need to puncture the baby's skin. This is a screening test, and a blood sample will be needed if your baby's bilirubin level is high.

Blood sample from a vein

The health professional taking a sample of your blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then put on a bandage.

How It Feels

Blood sample from a heel stick

A brief pain, like a sting or a pinch, is usually felt when the lancet punctures the skin. Your baby may feel a little discomfort with the skin puncture.

Blood sample from a vein

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

Heel stick

There is very little chance of a problem from a heel stick. A small bruise may develop at the site.

Blood test

There is very little chance of a problem from having blood sample taken from a vein.

  • You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
  • In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
  • Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

Results

A bilirubin test measures the amount of bilirubin in a blood sample. The results are usually available in 1 to 2 hours.

Normal adult values

Normal values may vary from lab to lab.

Bilirubin levels in adults
Bilirubin type Bilirubin level

Total bilirubin

0.3–1.0 mg/dL or 5.1–17.0 mmol/L

Direct bilirubin

0.1–0.3 mg/dL or 1.7–5.1 mmol/L

Indirect bilirubin (total bilirubin level minus direct bilirubin level)

0.2–0.8 mg/dL or 3.4–12.0 mmol/L

High values

  • High levels of bilirubin in the blood may be caused by:
    • Some infections, such as an infected gallbladder, or cholecystitis.
    • Some inherited diseases, such as Gilbert's syndrome, a condition that affects how the liver processes bilirubin. Although jaundice may occur in some people with Gilbert's syndrome, the condition is not harmful.
    • Diseases that cause liver damage, such as hepatitis, cirrhosis, or mononucleosis.
    • Diseases that cause blockage of the bile ducts, such as gallstones or cancer of the pancreas.
    • Rapid destruction of red blood cells in the blood, such as from sickle cell disease or an allergic reaction to blood received during a transfusion (called a transfusion reaction).
    • Medicines that may increase bilirubin levels. This includes many antibiotics, some types of birth control pills, indomethacin (Indocin), phenytoin (Dilantin), diazepam (Valium), and flurazepam (Dalmane).

Low values

Low levels of bilirubin in the blood may be caused by:

  • Medicines that may decrease bilirubin levels. This includes vitamin C (ascorbic acid), phenobarbital, and theophylline (Elixophyllin).

Normal values in newborns

Normal values in newborns depend on the age of the baby in hours and whether the baby was premature or full term. Normal values may vary from lab to lab.

Total bilirubin levels in newborns less than 7 days old
Age Premature baby Full-term baby

Less than 24 hours

Less than 8.0 mg/dL or less than 137 mmol/L

Less than 6.0 mg/dL or less than 103 mmol/L

Less than 48 hours

Less than 12.0 mg/dL or less than 205 mmol/L

Less than 10.0 mg/dL or less than 170 mmol/L

3 to 5 days

Less than 15.0 mg/dL or less than 256 mmol/L

Less than 12.0 mg/dL or less than 205 mmol/L

7 days or older

Less than 15.0 mg/dL or less than 256 mmol/L

Less than 10.0 mg/dL or less than 170 mmol/L

 

Bilirubin levels that may require treatment in a full-term, healthy baby
Baby's age Bilirubin level

24 hours or younger:

More than 10 mg/dL or more than 170 mmol/L

25 to 48 hours:

More than 15 mg/dL or more than 255 mmol/L

49 to 72 hours:

More than 18 mg/dL or more than 305 mmol/L

Older than 72 hours:

More than 20 mg/dL or more than 340 mmol/L

Note: A premature or sick baby with bilirubin levels lower than those listed above may need treatment.

A premature baby's liver is immature and may not be able to break down bilirubin properly in the blood. This is one of the reasons premature babies are more likely than full-term babies to develop jaundice.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful (except in newborns) include:

  • Caffeine, which can lower bilirubin levels.
  • Not eating for a long period (fasting), which normally increases indirect bilirubin levels.

What To Think About

  • A common cause of jaundice in newborns is a condition called physiologic jaundice. It occurs in healthy babies when they are 1 to 3 days old for several reasons, including the increased breakdown of red blood cells right after birth. It usually disappears on its own within a week without causing problems. However, in some cases, a baby with physiologic jaundice may need treatment with special lights (phototherapy) to prevent serious problems.
  • Bilirubin can be measured in amniotic fluid if your doctor thinks that your unborn baby may have a condition that destroys red blood cells (erythroblastosis fetalis). For more information, see the medical test Amniocentesis.
  • Bilirubin may also be measured in the urine. Normally urine does not contain any bilirubin. If bilirubin is detected in urine, additional testing may be needed to determine the cause. High amounts of bilirubin in urine may indicate that the bilirubin is not being removed from the body by the liver.
  • Using a transcutaneous bilirubin test, doctors can screen all newborns for jaundice. They place a device gently against the skin to check bilirubin levels before a baby goes home from the hospital.

References

Other Works Consulted

  • Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.

Credits

Author Debby Golonka, MPH
Editor Susan Van Houten, RN, BSN, MBA
Associate Editor Tracy Landauer
Primary Medical Reviewer Michael J. Sexton, MD - Pediatrics
Specialist Medical Reviewer Thomas Emmett Francoeur, MDCM, CSPQ, FRCPC - Pediatrics
Last Updated May 27, 2008

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