Gamma-Glutamyl Transferase

A typical reference range for GGT is roughly 9-48 U/L, though the upper limit varies by lab and tends to run a little higher in men than women. GGT (gamma-glutamyl transferase) is a liver and bile-duct enzyme and is one of the more sensitive markers on a liver panel. Compare your result to the reference range on your own report.

The most common drivers of a raised GGT are alcohol intake and fatty liver, followed by bile-duct obstruction and certain medications. GGT is particularly sensitive to alcohol, which is why it is often the first liver enzyme to rise with regular drinking. A high GGT with normal other liver tests frequently points toward alcohol or fatty liver.

GGT is useful for telling whether a high alkaline phosphatase (ALP) is coming from the liver or from bone. If both ALP and GGT are elevated, the source is likely the liver or bile ducts; if ALP is high but GGT is normal, the ALP is more likely bone-derived. This pairing is why the two enzymes are often read together.

Yes. Intense weight training can raise AST and ALT because those enzymes also leak from skeletal muscle, which can look like a liver problem when it is not. GGT is not found in muscle, so a normal GGT alongside raised AST and ALT strongly suggests the elevation is muscle-related rather than liver damage. It makes GGT a helpful tie-breaker for athletes, though your physician interprets the full picture.