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Epigallocatechin Gallate (EGCG) Side Effects & Safety

Evidence:Moderate
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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 — the most serious concern; high-dose EGCG (especially fasted) has caused liver injury in multiple case reports and the USP has flagged this risk
  • GI symptoms (nausea, stomach upset, constipation)
  • Insomnia and anxiety if product contains caffeine
  • Iron absorption reduction — EGCG chelates non-heme iron; separate from iron-rich meals or iron supplements by 2+ hours
  • Headache at high doses

Drug & Supplement Interactions

  • Iron supplements and iron-rich foods — EGCG significantly reduces non-heme iron absorption; separate by 2+ hours
  • Warfarin — green tea contains vitamin K and may reduce warfarin efficacy
  • Nadolol and other beta-blockers — EGCG may reduce nadolol absorption and efficacy
  • Bortezomib (cancer drug) — EGCG directly inactivates this proteasome inhibitor; contraindicated
  • Hepatotoxic medications — avoid combining high-dose EGCG with other liver-stressing drugs

Maximum Dose

Do not exceed: 800mg EGCG/day (liver toxicity risk increases significantly above this level on an empty stomach)

Full Epigallocatechin Gallate (EGCG) Guide

References

  1. ReviewHuang J, Wang Y, Xie Z, et al. (2014). The anti-obesity effects of green tea in human intervention and basic molecular studies. European Journal of Clinical Nutrition. DOI PubMed
  2. ObservationalKuriyama S, Shimazu T, Ohmori K, et al. (2006). Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan. JAMA. DOI PubMed
  3. ReviewMazzanti G, Di Sotto A, Vitalone A (2015). Hepatotoxicity of green tea: an update. Archives of Toxicology. DOI PubMed
  4. Meta-analysisZhang Y, Xu Q, Hu J, Zhang F, et al. (2025). Green Tea and Epigallocatechin Gallate (EGCG) for Cancer Prevention: A Systematic Review and Meta-Analysis.. The American journal of Chinese medicine. DOI PubMed
  5. Cunningham 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
  6. Zhu W, Jia L, Qiao Q, Li X, et al. (2026). Efficacy and safety of 7-day aerosolized epigallocatechin-3-gallate in oncologic patients with COVID-19 pneumonia.. BMC cancer. DOI PubMed
  7. Zafrilla P, Ballester P, Victoria-Montesinos D, Cerdá B, et al. (2025). Dietary Bioactive Compounds and Their Role in Allergy Prevention: A Comprehensive Review.. Nutrients. DOI PubMed
Show 5 more references
  1. Meta-analysisSaadh MJ, Gataa IS, Hussam AS, Kaur I, et al. (2025). Effect of Epigallocatechin Gallate on Glycemic Index: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. Clinical therapeutics. DOI PubMed
  2. Johnson JJ, Siblini H, Al-Hendy A, Segars JH, et al. (2025). Evaluating the Effect of Epigallocatechin Gallate (EGCG) in Reducing Folate Levels in Reproductive Aged Women by MTHFR and DHFR Genotype in Combination With Letrozole or Clomiphene.. Clinical and translational science. DOI PubMed
  3. Kaag S, Lorentz A (2023). Effects of Dietary Components on Mast Cells: Possible Use as Nutraceuticals for Allergies?. Cells. DOI PubMed
  4. Churm R, Williams LM, Dunseath G, Prior SL, et al. (2023). The polyphenol epigallocatechin gallate lowers circulating catecholamine concentrations and alters lipid metabolism during graded exercise in man: a randomized cross-over study.. European journal of nutrition. DOI PubMed
  5. Cieuta-Walti C, Cuenca-Royo A, Langohr K, Rakic C, et al. (2022). Safety and preliminary efficacy on cognitive performance and adaptive functionality of epigallocatechin gallate (EGCG) in children with Down syndrome. A randomized phase Ib clinical trial (PERSEUS study).. Genetics in medicine : official journal of the American College of Medical Genetics. DOI PubMed