Conjugated Bilirubin (“direct”) test

Once in the liver, bilirubin becomes “conjugated” or direct. This means it is water-soluble and can be excreted. Unconjugated bilirubin is toxic, but conjugated bilirubin is usually not, because it can be removed from the body, as long as nothing is interfering with its removal. The conjugated (direct) bilirubin level is often elevated by alcohol, infectious hepatitis, drug reactions, and autoimmune disorders. Posthepatic disorders also can cause conjugated hyperbilirubinemia.

A normal level is: Direct (also called conjugated) bilirubin: less than 0.3 mg/dL (less than 5.1 µmol/L)

Elevated levels may indicate liver damage or disease. Higher than normal levels of direct bilirubin in your blood may indicate your liver isn't clearing bilirubin properly. One common, and harmless, cause of elevated bilirubin is Gilbert's syndrome, a deficiency in an enzyme that helps break down bilirubin.