Warfarin and Supplements: Important Interactions

Warfarin is one of the most interaction-sensitive medications in common use. It works by narrowing the margin of blood clotting, and many other substances -- including several common supplements -- can shift that margin in either direction. This makes warfarin a genuinely high-stakes case for checking before combining.

Documented interaction findings

• Warfarin + sertraline (caution, high evidence) -- named directly on warfarin's own FDA label, in its table of drugs that can increase bleeding risk, under serotonin reuptake inhibitors.
• Warfarin + omeprazole (caution, high evidence) -- omeprazole's label has a dedicated warfarin subsection documenting increased INR and bleeding risk, with an explicit monitoring recommendation.
• Warfarin + turmeric (mixed evidence) -- the available evidence for this pair is mixed rather than clearly one-directional; see warfarin's medication page for the full, transparently-caveated detail.

Why supplements matter so much here

Several supplements independently affect bleeding risk or vitamin K metabolism (which warfarin directly depends on), so even a supplement with no documented interaction against warfarin specifically is worth checking rather than assuming. This is precisely the kind of medication where "natural" supplement marketing claims should not substitute for checking the actual evidence.

What to do

Never start, stop, or change a warfarin dose based on this site. INR monitoring and dose changes require a prescriber. If you are on warfarin and considering any new supplement, check it first and bring the result to your next appointment or a pharmacist conversation.

See Important Interactions for every currently reviewed caution/monitor pair across the whole catalog, not just warfarin.