Enzyme that indicates liver and bile duct health
13 of 22 providers
Liver Function
9-48 U/L
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.
| Range Type | Level | Significance |
|---|---|---|
| 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 Elevated | Men: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 Elevated | 50-150 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. |
Complete abstinence:Most effective approach. GGT typically normalizes within 2-4 weeks of abstinence in alcohol-related elevation
Reduce to minimal intake:If elevated, aim for zero or <2 drinks per week. Even moderate drinking (3-7 drinks/week) can keep GGT elevated
N-acetylcysteine (NAC):600-1200 mg daily helps replenish glutathione and may accelerate GGT normalization after alcohol cessation
Milk thistle (silymarin):140-280 mg 2-3x daily supports liver regeneration and alcohol-related damage
Monitor response:Retest GGT 4-8 weeks after reducing/eliminating alcohol to confirm it was the cause
Weight loss:7-10% body weight reduction significantly lowers GGT in overweight/obese individuals with fatty liver
Mediterranean diet:Emphasize olive oil, fish, vegetables, legumes, whole grains. Reduces liver fat and inflammation
Reduce refined carbohydrates:Limit sugar, high-fructose corn syrup, white bread, sugary beverages
Increase omega-3 intake:2-4g EPA+DHA daily or fatty fish 3x/week reduces liver inflammation
Coffee:2-3 cups daily associated with lower GGT and reduced liver disease progression
Review medications:Common GGT-elevating drugs include phenytoin, barbiturates, carbamazepine, oral contraceptives, NSAIDs, statins, and many antibiotics
Eliminate hepatotoxic substances:Anabolic steroids, excessive supplements, recreational drugs
Avoid acetaminophen excess:Limit to <3000 mg/day;lower if drinking alcohol or taking other medications
Reduce environmental toxins:Minimize pesticide exposure, industrial chemicals, harsh cleaning products
Herbal supplements:Many marketed for liver health can paradoxically cause injury (green tea extract, kava, comfrey)
N-acetylcysteine (NAC):600-1200 mg daily. Precursor to glutathione, the body's master antioxidant. Particularly helpful if GGT elevated
Glutathione (liposomal):500-1000 mg daily. Direct supplementation with high-bioavailability forms
Vitamin C:500-1000 mg daily supports glutathione recycling and antioxidant defense
Selenium:200 mcg daily (from selenomethionine). Cofactor for glutathione peroxidase enzyme
Alpha-lipoic acid:300-600 mg daily. Regenerates glutathione and other antioxidants
Regular exercise:150+ minutes/week moderate aerobic activity reduces GGT independent of weight loss
Adequate sleep:7-9 hours nightly. Poor sleep worsens metabolic dysfunction and liver inflammation
Stress management:Chronic stress elevates cortisol and inflammatory markers, worsening metabolic liver disease
Support bile flow:Artichoke extract, dandelion root, bitter greens (arugula, endive) support healthy bile production
Intermittent fasting:Time-restricted eating (16:8) or alternate-day fasting improves metabolic health and reduces liver fat
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.
Source:Fraser A, et al. Gamma-glutamyltransferase is associated with incident vascular events independently of alcohol intake. Heart. 2007;93(9):1121-1125.
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.
Source:Lee DH, et al. Gamma-glutamyltransferase and metabolic syndrome, diabetes, and cardiovascular disease. Arterioscler Thromb Vasc Biol. 2007;27(1):127-133.
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.
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.
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.
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | — | $349 | 65 |
 Labcorp OnDemand | — | $398 | 30+ |
| — | $486 | 40+ | |
| — | $468 | 83 | |
| ✓ | $349 | 100+ | |
 InsideTracker | ✓ | $680 | 54 |
 Function Health | ✓ | $365 | 100+ |
| ✓ | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| — | $399 | 100+ | |
| — | $Varies | 75+ | |
| — | $190 | 100+ | |
| — | $99 | 50 | |
| — | $125 | 60 | |
| — | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 129 |
13 providers include this biomarker in their panels
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
