Total and fractionated bilirubin

Bilirubin is formed as a result of the breakdown of the haemoglobin heme group. Its concentration is used in the evaluation of possible liver damage.

Fractionated bilirubin comprises two fractions: direct and indirect.

Direct or conjugated bilirubin  is produced in the liver, where it is conjugated with glucuronic acid. Its presence in high amounts indicates liver problems.

Unconjugated or indirect bilirubin is the fraction of bilirubin that has not yet been conjugated in the liver. Its presence in high amounts is related to problems in the degradation process of haemoglobin.