Is EGCG Green Tea Safe with Warfarin?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Avoid high-dose green tea extracts (>3 cups/day equivalent). Inform your anticoagulation provider of any green tea supplement use. Monitor INR more frequently if use continues.
Why this interaction occurs
High-dose EGCG can inhibit CYP2C9 and CYP3A4, reducing warfarin clearance and elevating INR. Paradoxically, very high doses may exert vitamin K-like activity reducing anticoagulant effect. The net result is unpredictable INR fluctuation.
Evidence
Evidence level: moderate.
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 134,328 reports mentioning Warfarin. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Warfarin + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All EGCG Green Tea interactions → · All Warfarin interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.