Gamma glutamyl transferase - plasma or serum

5 mL blood in lithium heparin or plain tube.

Increased levels are found in cholestatic liver disease and in hepatocellular disease when there is an element of cholestasis.

Levels are increased in diabetes, with chronic intake of excess alcohol and with certain drugs (especially phenytoin) as a result of enzyme induction.

Pancreatitis and prostatitis may also be associated with increased levels.

Levels may be normal early in the course of acute hepatocellular damage eg, acute viral hepatitis, paracetamol hepatotoxicity.