Q. Recently I had to increase my dose of warfarin by one mg. On the label it said avoid cranberry juice but I’ve not seen this on previous warfarin prescriptions. I have atrial fibrillation and that is why I take the anticoagulant.
A. Warfarin (Coumadin) is a blood thinner that prevents blood clots that may lead to a stroke. The dose is critical as too little medicine may permit a blood clot to form while too much could lead to hemorrhaging.
Many foods and drugs interact with warfarin. Several years ago there was a warning that cranberry juice might be among them. Anecdotal reports suggested that cranberry juice might increase the effectiveness of warfarin and cause bleeding.
A review in the American Journal of Medicine (May, 2010) analyzed data from randomized clinical trials and concluded that cranberry juice does not pose a threat when consumed in moderation. Cranberry capsules or concentrate may be another matter. Periodic monitoring is advised for anyone on warfarin.