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Bilirubin test

What is a bilirubin test?

A bilirubin test measures the level of bilirubin in the blood. Bilirubin results in the body when older red blood cells are destroyed.

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It is the function of the liver to process bilirubin so that it can be excreted from the body. Normally a blood test is conducted to test levels of bilirubin in the body, though a urine test can also be conducted.

Bilirubin exists in two forms - direct and indirect bilirubin. Indirect bilirubin is the form where it is yet to reach the liver and has not been processed. Direct bilirubin has been changed by the liver into a water soluble form so that it can be reabsorbed or excreted.  The bilirubin test measures total bilirubin and direct bilirubin with the while the difference between the two is considered to be the level of indirect bilirubin.

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Why is it conducted?

Though in itself high bilirubin levels are not dangerous for adults, they do indicate certain diseases and should always be followed up by a health professional.

  • This test can give a fair idea of the different kinds of liver problems like jaundice, hepatitis and cirrhosis as bilirubin is processed in the liver itself before being excreted in the feces.
  • It can also help to determine obstruction in bile ducts due to stones, tumor or cancer.
  • As bilirubin is actually a byproduct of routine break down of old red blood cells in the body, it can also help to pinpoint any increase in the rate of their destruction. It is therefore indicative of blood problems.
  • The bilirubin test is extremely critical for newborn babies as high levels of bilirubin can even lead to brain damage among other things.

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Who should go for it?

  • People who have yellowing of skin and eyes and are suspected to be suffering from jaundice.
  • People with liver cirrhosis or hepatitis to gauge the progress of their treatment
  • Newborn babies with suspected jaundice to determine the necessity for phototherapy.
  • Some medications like paracetamol in high doses, NSAIDs and isoniazid adversely affect liver functions and it is advisable to have a bilirubin test for drug toxicity.
  • People with excessive alcohol consumption.
  • People suffering from certain blood problems like anemia that does not arise from iron deficiency.

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Procedure

This is a simple blood test and blood will be taken from a vein in the arm. You do not need to make any preparations for it. For babies a heel stick is used to draw blood from the heel of the baby.

For newborn babies, a TcB (transcutaneous bilirubin) test can be used for initial screening that precludes the necessity of a blood test in babies with normal bilirubin levels.

Interpretation of results

The testing laboratory always provides the reference range for the bilirubin test as it can vary for different labs. Besides, certain medicines can affect bilirubin levels and therefore should be taken into consideration while interpreting test results.

The normal range is as follows:

  • Total bilirubin: 0.3 to 1.9 mg/dl
  • Direct bilirubin: up to 0.3 mg/dl

Written by: Nandita tripati
Date last updated: January 07, 2015