Food and medicine interaction
Cranberry juice and cranberry supplements and warfarin
ProbableEvidence level: probable. Case reports in people plus a known mechanism, but no controlled studies.
Last reviewed
What can happen
Case reports linked cranberry with raised INR and bleeding, but a randomized double-blind trial of 240 mL of cranberry juice a day for two weeks found no change in warfarin levels and no clinically important change in INR. NCCIH calls the evidence conflicting.
- Why it happens
- Cranberry flavonoids were suspected of affecting warfarin metabolism (CYP2C9), but the controlled trial excluded a pharmacokinetic interaction.
- At ordinary food amounts
- A glass a day did not change INR in the controlled trial. Large amounts and concentrated supplements are less studied.
What to do
If you take warfarin, tell your anticoagulation clinic before starting daily cranberry juice or supplements, and keep your intake steady.
Never stop or change a prescribed medicine without talking to the prescriber.
Common questions
Can I have cranberry juice and cranberry supplements while taking anticoagulants?
If you take warfarin, tell your anticoagulation clinic before starting daily cranberry juice or supplements, and keep your intake steady. A glass a day did not change INR in the controlled trial. Large amounts and concentrated supplements are less studied.
Sources
- Ansell J, et al. The absence of an interaction between warfarin and cranberry juice: a randomized, double-blind trial. J Clin Pharmacol. 2009. PMID 19553405.
- National Center for Complementary and Integrative Health. Cranberry: Usefulness and Safety.
- Tan CSS, Lee SWH. Warfarin and food, herbal or dietary supplement interactions: a systematic review. Br J Clin Pharmacol. 2021. PMID 32478963.
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