Supplement–Drug Interaction Lookup
Choose a prescription medicine to see which supplements interact with it, ranked from "avoid" to "good to know".
8 supplement interactions with Warfarin
Vitamin K Avoid combining
Vitamin K directly counteracts warfarin. Don't start or stop it without your prescriber; keep intake consistent.
St. John's wort Avoid combining
Can reduce warfarin's effect and raise clot risk.
Fish oil Use caution
High doses may increase bleeding risk. Ask your doctor before taking more than 1–2 g/day.
Ginkgo Use caution
May increase bleeding risk.
Vitamin E Use caution
High doses may increase bleeding risk.
Turmeric Use caution
High-dose turmeric or curcumin may increase bleeding risk.
Garlic Use caution
Garlic supplements may increase bleeding risk.
CoQ10 Use caution
CoQ10 may reduce warfarin's effect. Ask your prescriber before starting.
Frequently asked questions
Which supplements interact with blood thinners?
Vitamin K, St. John's wort, and high doses of fish oil, ginkgo, vitamin E, turmeric and garlic can affect warfarin or bleeding risk. Ask your prescriber before starting any of them.
Can supplements make birth control fail?
St. John's wort can make hormonal contraceptives less effective. Tell your clinician about every supplement you take.
Sources
Free tool for education only. It doesn't replace advice from your doctor or pharmacist.