Bilirubin

Bilirubin is a compound that is produced when red blood cells are broken down. Due to its distinctive orange or yellow colour, a build-up of bilirubin in the blood can lead to jaundice (yellowing of the skin).

A bilirubin test is a type of blood test that helps measure liver function. In the context of HIV infection, it is often used to monitor for toxicity to antiretroviral therapy or to help assess liver function in people with viral hepatitis co-infection. The bilirubin test is also used in the diagnosis or monitoring of a wide range of blood and liver conditions.

A blood sample is drawn from a vein in the arm and analysed in the lab. If available, a transcutaneous bilirubin meter can non-invasively measure bilirubin simply by being placed on the skin. A urine dip test can indicate elevated bilirubin, but a blood test is needed to establish an exact level. 

Total serum bilirubin (the total amount of bilirubin in the blood) is normally less than 20 µmol/L (1.2 mg/dL).

Elevated bilirubin indicates either a blockage in the way bilirubin is cleared from the blood by the liver or a breakdown of red blood cells. Causes may include liver disease, blood disease, or drug toxicity. Some people may be genetically prone to bilirubin elevations when taking the protease inhibitor atazanavir (Reyataz). In a person taking antiretroviral drugs, high bilirubin may lead to a review of drug treatment and a possible dose reduction.