Is St. John's Wort Safe with warfarin sodium?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Avoid St. John's Wort while taking warfarin. If you start or stop taking it, notify your doctor immediately for more frequent INR monitoring.
Why this interaction occurs
St. John's Wort may decrease the anticoagulant effects of warfarin sodium and can interact through CYP450 interactions, potentially reducing warfarin exposure and increasing clotting risk.
Evidence
Evidence level: strong.
Data source
FDA Drug Label
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 3,390,437 reports mentioning warfarin sodium. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the warfarin sodium + 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 St. John's Wort interactions → · All warfarin sodium interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.