GGT (Gamma-glutamyl transferase)

GGT (gamma-glutamyl transferase) is an enzyme anchored in cell membranes that helps recycle glutathione, your body's master antioxidant. It is most active in your liver, bile ducts, and kidneys. Serum GGT rises with bile blockage (cholestasis), alcohol, fatty liver, and many enzyme-inducing drugs, which makes it a sensitive but unspecific liver marker. There is more to it, though. Even within the normal range, a higher GGT is independently linked to insulin resistance, heart disease, and higher death from all causes, likely as a sign of oxidative stress.

Last reviewed: June 22, 2026

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