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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 colour.
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.
Mild jaundice in newborns usually does not cause problems. But too much bilirubin (hyperbilirubinemia) in a newborn baby can cause brain damage (kernicterus) and other serious problems. So some babies who develop jaundice may need treatment to lower their bilirubin levels.
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, tumours 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.
- Are or might be pregnant.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form .
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 metre to check a newborn's bilirubin level. This small hand-held 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.
There is very little chance of a problem from a heel stick. A small bruise may develop at the site.
There is very little chance of a problem from having a 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.
A bilirubin test measures the amount of bilirubin in a blood sample. The results are usually available in 1 to 2 hours.
Normal values in adults
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
0.0–0.3 mg/dL or 1.7–5.1 mcmol/L
0.2–1.2 mg/dL or 3.4–20.5 mcmol/L
- 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, diazepam (Valium), flurazepam, indomethacin, and phenytoin (Dilantin).
Low levels of bilirubin in the blood may be caused by:
- Medicines that may decrease bilirubin levels. This includes vitamin C, phenobarbital, and theophylline.
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.
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
- 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 topic Amniocentesis.
- Bilirubin may also be measured in the urine in some cases. 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. For more information, see the topic Jaundice in Newborns.
- Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
Other Works Consulted
- Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
Current as of:
September 23, 2020
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Brian D. O'Brien MD - Internal Medicine
Adam Husney MD - Family Medicine
Martin J. Gabica MD - Family Medicine
W. Thomas London MD - Hepatology
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