Is my GGT (Gamma-Glutamyl Transferase) normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal GGT level?
GGT is primarily a marker of cellular oxidative stress and glutathione depletion. While commonly associated with alcohol use, elevated GGT reflects broader metabolic strain — it is an independent predictor of cardiovascular disease, diabetes, and all-cause mortality even within standard "normal" ranges. Normal is 9-48 U/L, but longevity optimal is strictly < 25 U/L. GGT rises with metabolic syndrome, obesity, biliary obstruction, and oxidative stress, making it one of the most underutilized prognostic biomarkers in routine blood work.
| Range | Values |
|---|---|
| Standard Reference | 9–48 U/L |
| Longevity Optimal | < 25 U/L |
| High Risk | > 80 U/L |
What causes abnormal GGT levels?
Elevated GGT is caused by alcohol consumption (the most sensitive enzymatic alcohol marker), obesity and metabolic syndrome, non-alcoholic fatty liver disease (MASLD), medications (anticonvulsants, barbiturates, acetaminophen, statins), biliary obstruction (gallstones, tumors), hepatitis, pancreatitis, diabetes, and heart failure. Even moderate alcohol consumption (1-2 drinks/day) can elevate GGT.
When should you see a doctor?
See your doctor if GGT is above 80 U/L, or if GGT is elevated alongside ALT and AST (suggests active liver inflammation). If GGT is the only elevated liver enzyme, investigate alcohol intake, medication effects, and metabolic syndrome. Persistent elevation warrants liver ultrasound.
GGT and longevity
GGT is emerging as one of the most powerful yet overlooked prognostic biomarkers. Large population studies (including the Framingham Heart Study) demonstrate that GGT independently predicts cardiovascular events, type 2 diabetes, metabolic syndrome, and all-cause mortality — even when levels are within the standard reference range. The mechanism involves GGT's role in glutathione catabolism: when GGT rises, it reflects increased oxidative stress and glutathione turnover, indicating that the body's primary antioxidant defense system is under strain. GGT also catalyzes LDL oxidation at the arterial wall, directly linking liver-derived oxidative stress to atherosclerotic plaque formation. For longevity optimization, keeping GGT below 25 U/L is increasingly recommended.
Where to get a GGT test
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Related biomarkers
These biomarkers are often tested alongside GGT for a more complete picture.
Frequently asked questions
What is a normal GGT level?
What causes elevated GGT?
Is GGT a cardiovascular risk marker?
Is GGT only about alcohol?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.