GGT
Also reported as: Gamma-glutamyl transferase · Gamma GT
A liver enzyme involved in glutathione metabolism, released with hepatobiliary stress or enzyme induction.
Upper bounds of 50–70 U/L are common and sit far above where risk associations begin.
Cohort data show risk rising from around 20 U/L in men and 15 U/L in women, well inside the reference range.
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Where the thresholds sit
| Band | Range (U/L) | Note |
|---|---|---|
| Optimal | < 20 | — |
| Acceptable | 20–35 | — |
| Borderline | 35–50 | — |
| Elevated | > 50 | — |
Why it matters
Better known as an alcohol marker, but its real interest for healthspan is as a sensitive early indicator of fatty liver and oxidative stress. GGT within the 'normal' range still predicts diabetes, cardiovascular disease and mortality in large cohorts — one of the clearest cases where the lab ceiling hides useful signal.
What raises it
- Alcohol, the classic cause
- Non-alcoholic fatty liver disease
- Obesity and insulin resistance
- Some medications, particularly anticonvulsants
- Biliary obstruction
What lowers it
- Alcohol abstinence
- Weight loss
- Coffee, consistently, in observational data
How to move it
- 1Four weeks without alcohol is the fastest and most informative test — GGT has a half-life of around two weeks.
- 2If it stays elevated while sober, look for fatty liver. An ultrasound or a FIB-4 score is the next step.
- 3Lose visceral fat.
- 4Interpret alongside ALT — the two together distinguish patterns better than either alone.
What moves this marker
Interventions on this site with evidence behind them for this specific marker. None of them replaces working out why yours is where it is.
What makes a single reading misleading
- Sensitive but not specific — many things raise it.
- Rises with enzyme-inducing drugs without indicating liver damage.
- A normal GGT does not exclude liver disease.
Sources
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Educational only. Reference ranges are not diagnostic thresholds and this page cannot account for your medical history, medication or symptoms. Discuss any result that concerns you with a qualified clinician. See our medical disclaimer.