Q. Is it true that you should not drink cranberry juice if you are on Coumadin to thin the blood?
A. Several years ago British regulatory authorities issued a warning to patients taking warfarin (Coumadin) not to drink cranberry juice. This combination was associated with excessive bleeding and one man died. An article in the British Medical Journal (BMJ) suggested that patients taking warfarin would be prudent to limit their cranberry juice consumption.
Since that initial publication, there have been other reports of interactions and contradictions. This interaction remains somewhat controversial. One study showed that two cups of cranberry juice a day did not lead to bleeding worries. But there is a case of a man who died after drinking a substantial amount of cranberry juice daily after two weeks. The cause was internal hemorrhage linked to an interaction with his blood thinner warfarin.
The most recent reference is another case report in which a person twice experienced elevated INR (a measure of blood thinning) after drinking cranberry juice cocktail.
Our standard reference for drug interactions, Drug Interaction Facts, recommends that people should avoid drinking large amounts of cranberry juice if they are on warfarin.
You can access our free Guide to Coumadin (Warfarin) Interactions here.