Q. I have had blood clots in my lungs, and I take Coumadin to prevent recurrences. When I drank 12 ounces of cranberry-grape juice, it sent my INR level to 16.4, compared to the previous day’s level of 6.5. Both levels are too high, but 16 could have killed me! Is there any data on this interaction?
A. Warfarin (Coumadin) is an anticoagulant that prevents blood clots. Patients on this drug walk a tightrope because it interacts with so many foods and other drugs. Too little medicine could lead to blood clots, while too much could cause a fatal hemorrhage.
A potential cranberry juice-warfarin interaction is highly controversial. Well-conducted studies have not revealed a problem (British Journal of Clinical Pharmacology, July, 2010). But doctors have reported several cases of INR elevation in people consuming cranberry juice or sauce (Consultant Pharmacist, Jan., 2012).
INR is a measure of anticoagulation. When it exceeds 5, your risk of bleeding rises. An INR of 16 might indeed be lethal.
You aren’t the only one who has had problems with cranberries. Helen offered this:
“Unfortunately, I wasn’t warned that there could be a conflict between warfarin and cranberries. Just short of 3 yrs ago, at 70 I had a hip replacement. Upon returing home I opened a can of cranberry sauce and over the period of a week, was weak. After the last bite and drop of juice were consumed, I read a warning about an interaction between cranberries and warfarin.
The nurse checked my blood and the INR number was high. I was gradually taken off the warfarin. Now I warn everybody I know of the problem. Most of the medical people weren’t aware of it. Thanks for giving me an opportunity to write and warn others.”
When it comes to warfarin (Coumadin), trying to keep vitamin K intake fairly constant from day to day is important. To do so, it helps to know how much vitamin K is in the foods we eat. We have listed a few of the most common in our free Guide to Coumadin Interactions.
