GGT (Gamma-Glutamyl Transferase)
Enzyme that indicates liver and bile duct health
13 of 22 providers
Liver Function
9-48 U/L
What is GGT (Gamma-Glutamyl Transferase)?
GGT (Gamma-Glutamyl Transferase) is a liver enzyme found on the surface of bile duct cells and liver cells. It plays a role in glutathione metabolism and is involved in transporting amino acids across cell membranes. GGT is the most sensitive marker for detecting bile duct damage, cholestasis (impaired bile flow), and alcohol-related liver injury.
Unlike other liver enzymes, GGT is exquisitely sensitive to alcohol consumption—even moderate drinking can significantly elevate GGT. It is also elevated in fatty liver disease, medication-induced liver injury, and chronic cholestatic conditions. GGT helps differentiate the source of ALP elevation:if both GGT and ALP are elevated, the source is liver;if only ALP is elevated, consider bone disease.
GGT has emerged as an independent cardiovascular risk marker. Studies show that elevated GGT predicts heart disease, stroke, metabolic syndrome, and mortality, even in people without obvious liver disease. This cardiovascular association likely reflects oxidative stress and chronic inflammation. Optimal GGT levels for longevity are much lower than conventional reference ranges—ideally under 25-30 U/L.
Why GGT Is Your Most Sensitive Liver and Metabolic Marker
- Most sensitive for alcohol:GGT elevates with regular alcohol consumption before other liver enzymes, making it the best screening tool for alcohol-related liver damage
- Bile duct sentinel:First enzyme to rise in cholestasis, biliary obstruction, or primary biliary cholangitis
- Differentiates ALP source:When ALP is elevated, GGT confirms if it is liver-related (both elevated) or bone-related (GGT normal)
- Cardiovascular risk predictor:Elevated GGT independently predicts heart disease, stroke, diabetes, and mortality, even at "normal"levels
- Oxidative stress marker:GGT elevation reflects glutathione depletion and increased oxidative stress, linked to metabolic disease and aging
Optimal vs Standard Ranges
Optimal (Longevity)Men:<25 U/L, Women:<20 U/L▼
- Associated with lowest cardiovascular risk, best metabolic health, and optimal longevity
- Studies show these levels correlate with reduced diabetes, heart disease, and all-cause mortality
- Target this range through lifestyle optimization, minimal alcohol, and metabolic health
Borderline ElevatedMen:25-50 U/L, Women:20-40 U/L▼
- Often within "normal"lab range but associated with increased metabolic and cardiovascular risk
- Indicates alcohol consumption, fatty liver, medication effects, or oxidative stress
- Warrants lifestyle modification:reduce alcohol, lose weight if overweight, optimize diet
- Retest in 3-6 months
Moderately Elevated50-150 U/L▼
- Indicates significant liver stress or damage
- Common causes include regular alcohol consumption, fatty liver disease, medication toxicity, or chronic cholestatic conditions
- Requires medical evaluation, liver imaging (ultrasound), and investigation of underlying cause
- If ALP also elevated, evaluate for biliary disease
Severely Elevated>150 U/L▼
- Indicates substantial liver injury or cholestatic disease
- Levels >200 U/L suggest heavy alcohol use, severe cholestasis, or significant liver disease
- Requires urgent workup including ALT, AST, ALP, bilirubin, hepatitis panel, and imaging
- If ALP >3x normal with very high GGT, consider biliary obstruction or primary biliary cholangitis
- Very high GGT (>500) often seen with chronic heavy alcohol consumption
Scientific Evidence
GGT as Independent Cardiovascular Risk Marker
Large meta-analyses show that elevated GGT is an independent predictor of cardiovascular disease, stroke, and mortality, even after adjusting for traditional risk factors. Each doubling of GGT is associated with 30-40% higher cardiovascular risk. This relationship is continuous with no clear threshold—even "high-normal"GGT (30-50 U/L) confers increased risk.
GGT and Metabolic Syndrome
GGT is strongly associated with all components of metabolic syndrome (obesity, insulin resistance, dyslipidemia, hypertension). Elevated GGT predicts incident diabetes with similar accuracy to fasting glucose. The association reflects oxidative stress, chronic inflammation, and fatty liver disease common in metabolic dysfunction.
Alcohol Sensitivity of GGT
GGT is the most sensitive single marker for detecting alcohol consumption. Even moderate drinking (2-3 drinks daily) can elevate GGT, often before ALT or AST rise. GGT normalizes within 2-6 weeks of abstinence, making it useful for monitoring sobriety. Sensitivity for chronic heavy drinking is 70-85%.
Source:Whitfield JB, et al. Gamma glutamyl transferase. Crit Rev Clin Lab Sci. 2001;38(4):263-355. (PubMed)
GGT and Mortality in Healthy Populations
Even in apparently healthy individuals with GGT in the "normal"range, higher levels predict all-cause mortality. People in the highest quartile of "normal"GGT (40-50 U/L) have 50-70% higher mortality risk compared to lowest quartile (<20 U/L). This supports targeting optimal rather than merely "normal"GGT levels.
Source:Ruhl CE, et al. Relationship of serum gamma-glutamyltransferase levels to mortality in the United States:NHANES III. Hepatology. 2009;50(3):661-662.
NAC for GGT Reduction
N-acetylcysteine (NAC) supplementation replenishes glutathione stores and can reduce elevated GGT, particularly in contexts of oxidative stress or alcohol-related liver injury. Studies show 600-1200 mg daily NAC for 3-6 months can reduce GGT by 20-40% while improving liver function and antioxidant capacity.
Source:Khoshbaten M, et al. N-acetylcysteine improves liver function in patients with non-alcoholic fatty liver disease. Hepat Mon. 2010;10(1):12-16.
Which Providers Test GGT (Gamma-Glutamyl Transferase)?
Full Provider Comparison
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | — | $349 | 65 |
 Labcorp OnDemand | — | $398 | 30+ |
| — | $486 | 40+ | |
| — | $444 | 288 | |
| ✓ | $349 | 100+ | |
| ✓ | $761 | 54 | |
 Function Health | ✓ | $365 | 160+ |
| ✓ | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| ✓ | $375 | 80+ | |
| — | $Varies | 75+ | |
| — | $190 | 100+ | |
| — | $99 | 50 | |
| — | $124 | 60 | |
| — | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 70-80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 128 |
Frequently Asked Questions
What is GGT (Gamma-Glutamyl Transferase)?
Enzyme that indicates liver and bile duct health
What is the optimal range for GGT (Gamma-Glutamyl Transferase)?
The standard reference range for GGT (Gamma-Glutamyl Transferase) is 9-48 U/L. Optimal ranges may differ based on individual health goals and expert recommendations.
Which blood test providers include GGT (Gamma-Glutamyl Transferase)?
13 out of 22 blood testing providers include GGT (Gamma-Glutamyl Transferase) in their panels. This biomarker is widely available across major providers.
What category does GGT (Gamma-Glutamyl Transferase) fall under?
GGT (Gamma-Glutamyl Transferase) is categorized under Liver Function. This category includes biomarkers that help assess related aspects of health and wellness.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed:2026-02-20