Gilbert's syndrome or familial benign unconjugated hyperbilirubinaemia is a heritable disorder of bilirubin metabolism, found in about 5% of the population. The syndrome produces an elevated level of unconjugated bilirubin in the bloodstream but normally has no other effect. Rarely, mild jaundice may appear. There is some evidence that Gilbert's syndrome also reduces the liver's ability to detoxify certain chemicals; it may be wise to avoid drugs that tax liver function, such as acetaminophen.
While this syndrome is considered harmless, it is clinically important because it may be confused with much more dangerous liver conditions. However, these will show other indicators of liver dysfunction. Haemolysis can be excluded by a full blood count.
Gilbert's syndrome is thought to be caused by a deficiency in the enzyme glucuronosyltransferase. It was first described by Augustin Nicolas Gilbert and co-workers in 1900.