What does the Gamma-Glutamyl Transferase test measure?

Why is Gamma-Glutamyl Transferase measured?

GGT is a sensitive but non-specific marker of hepatobiliary disease and is most valuable in clarifying the source of an elevated alkaline phosphatase. A raised GGT alongside a raised ALP points to a hepatobiliary rather than a skeletal origin. It is also a sensitive indicator of cholestasis, enzyme induction by alcohol or medication, and, increasingly, a marker associated with metabolic and cardiovascular risk. Its lack of specificity means it is interpreted in context rather than as a standalone diagnostic.

Reference ranges

Standard reference

Adult males: 8–61 U/L; adult females: 5–36 U/L # REVIEWER FLAG: Reference intervals are sex- and assay-dependent — reviewer to confirm against Access Medical Laboratories' assay-specific ranges.

Functional medicine optimal

Low-normal GGT (below the population mean) is associated with lower metabolic and cardiovascular risk in observational studies # REVIEWER FLAG: 'Optimal' low-GGT association is observational and not a clinical target — reviewer to confirm framing.

Units

U/L, IU/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.