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Green Tea Extract Side Effects & Safety

Evidence:Strong
·

This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Safe with Caution

Potential Side Effects

  • Hepatotoxicity risk — rare but serious liver injury reported with high-dose extracts (>800mg EGCG/day), especially on empty stomach; EFSA issued safety guidance
  • Caffeine-related effects (insomnia, anxiety, jitteriness) unless using decaffeinated extract
  • GI discomfort (nausea, stomach pain) especially on empty stomach
  • Iron absorption reduction — catechins chelate non-heme iron; separate from iron supplements by 2 hours

Drug & Supplement Interactions

  • Iron supplements — EGCG reduces non-heme iron absorption by up to 25%; take at different times
  • Stimulants and caffeine — additive stimulant effects if extract contains caffeine
  • Nadolol and other beta-blockers — green tea may reduce nadolol absorption by 85%
  • Warfarin — green tea contains vitamin K; large amounts may reduce anticoagulant effect
  • Hepatotoxic drugs — avoid combining high-dose GTE with other hepatotoxic medications

Maximum Dose

Do not exceed: Do not exceed 800mg EGCG daily; doses above this increase hepatotoxicity risk per EFSA safety assessment

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References

  1. Meta-analysisHaghighatdoost F, Hariri M (2019). The effect of green tea on inflammatory mediators: a systematic review and meta-analysis of randomized clinical trials. Phytotherapy Research. DOI PubMed
  2. Meta-analysisLin Y, Shi D, Su B, et al. (2020). The effect of green tea supplementation on obesity: a systematic review and dose-response meta-analysis of randomized controlled trials. Phytotherapy Research. DOI PubMed
  3. ReviewEFSA Panel on Food Additives and Nutrient Sources (2018). Scientific opinion on the safety of green tea catechins. EFSA Journal. DOI PubMed
  4. Meta-analysisAsbaghi O, Rezaei Kelishadi M, Larky DA, Bagheri R, et al. (2024). The effects of green tea extract supplementation on body composition, obesity-related hormones and oxidative stress markers: a grade-assessed systematic review and dose-response meta-analysis of randomised controlled trials.. The British journal of nutrition. DOI PubMed
  5. Meta-analysisAsbaghi O, Fouladvand F, Moradi S, Ashtary-Larky D, et al. (2020). Effect of green tea extract on lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysis.. Diabetes & metabolic syndrome. DOI PubMed
  6. Meta-analysisWang X, Tian J, Jiang J, Li L, et al. (2014). Effects of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of type 2 diabetes mellitus: a systematic review and meta-analysis of randomised controlled trials.. Journal of human nutrition and dietetics : the official journal of the British Dietetic Association. DOI PubMed
  7. Meta-analysisBaladia E, Basulto J, Manera M, Martínez R, et al. (2014). [Effect of green tea or green tea extract consumption on body weight and body composition; systematic review and meta-analysis].. Nutricion hospitalaria. DOI PubMed
Show 5 more references
  1. ReviewWiese F, Kutschan S, Doerfler J, Mathies V, et al. (2023). Green tea and green tea extract in oncological treatment: A systematic review.. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition. DOI PubMed
  2. ReviewMaleki V, Taheri E, Varshosaz P, Tabrizi FPF, et al. (2021). A comprehensive insight into effects of green tea extract in polycystic ovary syndrome: a systematic review.. Reproductive biology and endocrinology : RB&E. DOI PubMed
  3. ReviewHu J, Webster D, Cao J, Shao A (2018). The safety of green tea and green tea extract consumption in adults - Results of a systematic review.. Regulatory toxicology and pharmacology : RTP. DOI PubMed
  4. RCTCunningham A, Gomes A, Meng L, Shapses S, et al. (2026). Effects of Green Tea Extract Supplementation on Inflammatory Cytokines Among Postmenopausal Women with Overweight or Obesity-A Secondary Analysis of a Randomized Controlled Trial.. Nutrients. DOI PubMed
  5. RCTDemirli A, Ulupınar S, Terzi M, Özbay S, et al. (2025). Synergistic Effects of Green Tea Extract and Ginger Supplementation on Endurance Performance and Thermal Perception in Normothermic and Cold Environments: A Randomized, Placebo-Controlled, Double-Blind Crossover Trial.. Nutrients. DOI PubMed