Is Milk Thistle Safe with Warfarin?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Monitor INR more frequently if starting or stopping Milk Thistle. Do not adjust warfarin dose without consulting your healthcare provider. Report any unusual bleeding or bruising immediately.
Why this interaction occurs
Silymarin (active component of Milk Thistle) inhibits CYP2C9, the primary enzyme responsible for warfarin metabolism. This can reduce warfarin clearance and elevate plasma levels, increasing bleeding risk. Milk Thistle also inhibits P-glycoprotein, further affecting warfarin disposition.
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 Milk Thistle interactions → · All Warfarin interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.