Bilirubin

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Also known as: Total bilirubin, conjugated or direct bilirubin, unconjugated or indirect bilirubin
Related tests: AST, ALT, ALP, GGT, liver function tests

At a Glance

Why Get Tested?

To screen for and monitor liver disorders, such as cirrhosis. To help detect certain rare genetic disorders in sick babies and to avoid brain damage in babies who are markedly jaundiced.

When to Get Tested?

If your doctor thinks you have symptoms or signs of liver damage, liver disease, bile duct blockage, haemolytic anaemia or a liver-related metabolic problem.

Sample Required?

In adults, a blood sample from a vein in the arm; in newborns, a blood sample from a heel-prick

Test Preparation Needed?

No test preparation is necessary. The blood sample should ideally be protected from bright light before analysis.

The Test Sample

What is being tested?

Bilirubin is an orange-yellow pigment found in bile. The normal life-span of red blood cells in the circulation is 120 days. When they are broken down the pigment giving them their characteristic red colour, haemoglobin, (whose role is to carry oxygen to the tissues) is converted to unconjugated bilirubin. Only small amounts of bilirubin are normally present in the blood. Unconjugated bilirubin is not water soluble so it binds to a protein in the blood which then carries it to the liver. Within the liver, each unconjugated bilirubin molecule has a sugar molecule attached to it to form water soluble conjugated bilirubin. This is secreted into bile and carried to the intestine where bacteria break it down, eventually producing the brown pigment that colours normal stools.

How is the sample collected for testing?

In adults, blood is collected by needle from a vein in the arm. In newborns, a few drops of blood are usually collected from a heel-prick. Sometimes in newborns bilirubin is estimated by placing an instrument on the skin (a transcutaneous bilirubin meter).

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is necessary. The blood sample should ideally be protected from bright light before analysis.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.