GGT
A liver enzyme sensitive to bile flow problems, alcohol and oxidative stress.
| Typical reference range (male) | 3–70 U/L |
| Typical reference range (female) | 3–50 U/L |
| Commonly cited optimal range | below 25 U/L |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Gamma-glutamyl transferase sits on cell membranes, especially in the liver and bile ducts, and helps recycle glutathione, the body's main antioxidant.
Why it matters
GGT is a sensitive marker of liver and bile duct stress and confirms a liver source for elevated ALP. Even within the normal range, higher GGT is associated with alcohol intake, fatty liver, insulin resistance, cardiovascular disease and mortality.
What a high result can mean
Elevations occur with alcohol use, fatty liver disease, bile duct obstruction, hepatitis and enzyme-inducing medications (phenytoin, carbamazepine, barbiturates). Obesity, smoking and diabetes are also associated with higher values.
What a low result can mean
Low GGT is not a concern and generally indicates low oxidative and alcohol-related stress.
What affects the result
GGT responds to alcohol within weeks and falls over 2-4 weeks of abstinence, so it is used to monitor drinking. Weight loss and reducing alcohol lower it. Interpret alongside ALT, AST and ALP.
Units and conversion
Usually reported in U/L.
- From IU/L: multiply by 1 to get U/L
- From ukat/L: multiply by 60 to get U/L
Also called on lab reports
Gamma-Glutamyl Transferase, Gamma Glutamyl Transferase, Gamma-Glutamyltransferase, GGTP, Gamma GT, Gamma-Glutamyl Transpeptidase
Related tests: Liver
This page is educational and does not replace advice from a healthcare professional.