Biomarker · Liver

GGT (gamma-glutamyl transferase)

Also known as: GGT, gamma GT, gamma-glutamyl transpeptidase

A membrane enzyme of bile-duct and liver cells that rises with cholestasis, alcohol and many medicines. On its own it is too non-specific to diagnose anything, but it confirms that a raised alkaline phosphatase comes from the liver rather than bone.

Open in the 3D explorerLiver anatomy
3D model of the Liver in the Anatomy Nexus anatomy atlas
Interactive 3D model: Liver. Orbit, zoom and click the structures.Load the 3D model
Also known as
GGT, gamma GT, gamma-glutamyl transpeptidase
Units
U/L (units per litre)
Measured by
Liver function tests

What it is and what it does

GGT transfers amino acid fragments across cell membranes and is abundant in the biliary tree, liver, kidney and pancreas. Its main practical value is as a companion to ALP: both rise in bile-duct obstruction, whereas ALP alone rises in bone disease and pregnancy. GGT is also induced by alcohol and by enzyme-inducing drugs such as phenytoin and carbamazepine, so a raised GGT with otherwise normal tests often reflects drinking, obesity or medication rather than liver damage. It does not fall quickly after stopping alcohol, taking several weeks to normalise.

Why it may be higher

  • Cholestasis of any cause (with ALP)
  • Alcohol use, especially regular heavy drinking
  • Non-alcoholic fatty liver disease, obesity, type 2 diabetes
  • Enzyme-inducing medicines (phenytoin, carbamazepine, rifampicin), some others
  • Pancreatitis, heart failure, chronic obstructive pulmonary disease

Why it may be lower

  • No clinical significance; low in some inherited conditions

A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.

What can affect the result

  • Alcohol in the preceding weeks
  • Medicines
  • Body weight
  • Smoking
Reference ranges. Reference intervals for this marker depend on the laboratory, the assay, the units, age, sex and pregnancy. Interpret a result against the interval printed on the laboratory report, not against a figure from the internet.
Educational content. A biomarker page explains what a substance is and why its level can change. It cannot determine the cause of your result: interpret a result using the range supplied by the laboratory that performed the test, with the clinician who ordered it.