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📰Read the full Green Tea Extract evidence review on GMJ News →Complete clinical article, references and updates on news.gmj.ge. This page is the structured safety summary.⚠ Patient on GTE supplement + fasting — highest hepatotoxicity risk. Take with food [2]
⚠ New fatigue, dark urine, or jaundice in a GTE user — check liver enzymes immediately [3]
⚠ EGCG inhibits iron absorption — separate from iron supplements by 2+ hours [1]
⚠ Patient on hepatotoxic drugs (statins, acetaminophen) + GTE — additive liver risk [3]
ℹ️ Not obtained from food. Not applicable — this is not obtained from food in meaningful amounts; supplementation is the practical route.
🔬 Lab interpreter
Recommended test
ALT, AST
ALT, AST
Reference range / target
Normal range
Normal range
Monitor for hepatotoxicity. ANY elevation = stop GTE [3].
Full lab monitoring ↓⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
Green tea DRINKING is safe and health-promoting. Green tea EXTRACT supplements cause dose-dependent hepatotoxicity — >100 case reports of liver injury, some fatal. EFSA warning: keep EGCG <800 mg/day from supplements. ALWAYS take with food (fasting increases risk). Modest weight loss effect (~1.3 kg). Just drink the tea instead [1] [2] [3].
1 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: See guidance
Green tea (1–2 cups) safe. GTE supplements: AVOID (hepatotoxicity + caffeine + folate interference) [1].
👦 Pediatric: See guidance
Not recommended. Hepatotoxicity risk applies to children. Caffeine content is also a concern [1].
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Standard dose
How to take
🍽 Timing: ALWAYS WITH FOOD. Never on an empty stomach (hepatotoxicity risk) [2].
💊 With food: Take with a substantial meal [2].
2 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['Standardized GTE (50% EGCG)', 'common', 'Standard extract. Verify EGCG content per capsule. Decaffeinated versions available [1].'] | Standard | Check label | |
| ['EGCG isolate', '', 'Pure EGCG. Higher hepatotoxicity risk due to concentrated dose [2].'] | Standard | Check label | |
| ['Matcha', '', 'Whole-leaf consumption. Lower EGCG per serving than supplements. Contains L-theanine [1].'] | Standard | Check label |
3 Common questions
Is green tea extract safe? ▼
Green tea DRINKING (3–5 cups/day) is safe and health-promoting. Green tea EXTRACT supplements carry a real hepatotoxicity risk — >100 case reports of liver injury, some requiring transplant [2] [3]. The risk is dose-dependent and increases when taken on an empty stomach. If supplementing, keep EGCG <800 mg/day and ALWAYS take with food.
Why does fasting increase liver risk? ▼
When GTE is taken on an empty stomach, EGCG absorption spikes to higher peak concentrations. The liver receives a bolus of EGCG that overwhelms detoxification capacity, generating reactive metabolites [2]. Food blunts the absorption peak, reducing hepatotoxic risk.
Can I just drink green tea instead? ▼
Yes — and it's safer. 3–5 cups/day provides 150–500 mg EGCG gradually over the day (no bolus). Tea also provides L-theanine, other catechins, and minerals. The epidemiological health benefits are from tea drinking, not supplements [1].
What about weight loss? ▼
Meta-analyses show GTE produces ~1.3 kg weight loss over 12 weeks — clinically modest [1]. The thermogenic effect is real but small (~3–4% increase in energy expenditure). Not a substitute for diet and exercise.
4 Clinical evidence
Strong
EGCG is a potent antioxidant and thermogenic agent in vitro and animal models [1]. Hepatotoxicity: >100 case reports of liver injury from GTE supplements, including liver failure requiring transplant. Dose-dependent, increased by fasting state. EFSA, USP, and Health Canada have issued safety warnings [2] [3]. HIGH
Moderate
Weight loss: meta-analyses show modest effect (~1.3 kg over 12 weeks) from EGCG's thermogenic properties [1]. Cardiovascular: green tea consumption (not supplements) associated with reduced CVD mortality in observational studies [1]. Cancer: observational associations (especially gastric and breast cancer in Asian populations) but no interventional proof [1]. MODERATE
Insufficient
5 Safety, toxicity & adverse events
Absolute contraindications
✕ Active liver disease — GTE-associated hepatotoxicity (DILI), especially concentrated extracts >800mg EGCG/day on empty stomach
Relative
⚠ Iron deficiency — EGCG chelates non-heme iron (take 2hr apart from iron-rich meals)
⚠ Caffeine sensitivity — GTE contains caffeine
⚠ Concurrent hepatotoxic drugs (statins, acetaminophen) — additive liver risk
⚠ Pregnancy — limit caffeine; high-dose catechins may affect folate metabolism
⚠ Concurrent nadolol or other beta-blockers — EGCG reduces nadolol bioavailability 85%
🚩 Red flags
● New jaundice or dark urine in GTE supplement user — liver injury emergency [3]
● Patient taking GTE on empty stomach — highest risk; switch to with-food dosing [2]
● Patient taking >800 mg EGCG/day — exceed EFSA safety threshold [2]
● Patient on multiple hepatotoxic agents + GTE — additive risk [3]
6 Interactions
Drug interactions
Hepatotoxic drugs (acetaminophen, statins, isoniazid) Major
Mechanism: Additive hepatotoxicity risk. GTE supplements cause dose-dependent liver injury. [3]
Effect: Increased risk of liver injury. [3]
Action: Avoid GTE supplements in patients on hepatotoxic medications. Green tea drinking is safe [3].
Iron supplements Moderate
Mechanism: EGCG chelates non-heme iron, reducing absorption by 20–40%. [1]
Effect: Reduced iron bioavailability. [1]
Action: Separate GTE/green tea and iron supplements by at least 2 hours [1].
Nadolol (beta-blocker) Moderate
Mechanism: EGCG inhibits OATP1A2 and OATP2B1 transporters, reducing nadolol absorption. [1]
Effect: Reduced nadolol efficacy (up to 85% reduction in one study). [1]
Action: Avoid green tea within 4 hours of nadolol dosing [1].
Supplement synergies
L-Theanine · 100–200 mg L-theanine
Naturally co-present in tea. L-theanine moderates caffeine jitteriness and adds calming effects [1].
Naturally co-present in tea. L-theanine moderates caffeine jitteriness and adds calming effects [1].
7 Regulatory
United States (FDA): Dietary supplement. GRAS as food ingredient. No specific liver warning requirement (unlike EU) [1].
European Union (EFSA): 2018 safety assessment: EGCG ≥800 mg/day from supplements raises concern for liver injury. Recommended not to exceed 800 mg EGCG/day from supplements [2].
USP: USP Dietary Supplement Standards include a caution label for GTE products regarding hepatotoxicity [3].
Health Canada: Requires liver warning labels on GTE supplements [3].
8 US supplement products
21
on-market products containing Green Tea Extract (NIH DSLD)
Brands carrying Green Tea Extract (2)
Click a brand to see its Green Tea Extract products.
9 Frequently paired with
10 Cite this page
Vancouver: Pkhakadze G. Green Tea Extract — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Aug 07]. Available from: https://supplement.ge/ingredients/green-tea-extract/
APA 7th: Pkhakadze, G. (2026). Green Tea Extract — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/green-tea-extract/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: February 2027
References: 3 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Green Tea Extract — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/green-tea-extract/ CC BY 4.0.
GP
Prof. G. Pkhakadze, MD, MPH, PhD
Professor of Public Health · Head of Department, DTMU
Editor-in-Chief, Georgian Medical Journal (ISSN 3088-4322)
Chair, Public Health Institute of Georgia · UEMS Public Health Section
Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG