GGT, gamma-glutamyl transferase, is an enzyme concentrated in the cells lining the small bile ducts of the liver, and to a lesser extent in the kidney and pancreas. Blood levels rise when bile flow is obstructed or when the enzyme's production is stimulated by substances the liver processes. It is the most sensitive of the routine liver enzymes, and also the least specific.
No readings for this marker yet.
Raised values most often point to obstructed or sluggish bile flow, to fatty liver disease, or to induction of the enzyme by regular alcohol intake or by medicines such as anticonvulsants. It is also a common incidental finding with excess body weight, diabetes, and heart failure. Low values carry no clinical meaning. Because the causes are so varied, an elevation is a signal to look at the rest of the liver panel with a doctor rather than a finding on its own.
Alcohol in the days before the draw is the single most common reason for an unexpected rise, and the enzyme falls only slowly, over weeks, after intake stops. Body weight and some prescribed medicines shift it independently of any liver disease. Its main practical use is next to alkaline phosphatase: a rise in both points at the bile ducts, while a normal GGT suggests the alkaline phosphatase is coming from bone.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.