Warfarin (Coumadin) diet: Which foods should I avoid?

Is it true that people taking warfarin (Coumadin) should avoid certain foods?

- Beth / Illinois

Mayo Clinic hypertension specialist Sheldon Sheps, M.D., and colleagues answer select questions from readers.

Answer

Warfarin (Coumadin) is a blood-thinning medication that helps treat and prevent blood clots. Certain foods can impair the effect of warfarin. For this reason, it's important to pay attention to your diet while taking this medication.

The main dietary concern related to taking warfarin has to do with the amount of vitamin K in your diet. Vitamin K plays an important role in blood clotting. Warfarin works to reduce clotting by diminishing the activity of vitamin K. Eating large amounts of vitamin K can counteract the benefits of warfarin.

Some doctors recommend a low-vitamin K diet for people taking warfarin. But the key is to be consistent about how much vitamin K you consume on a daily basis. Limit foods that are high in vitamin K, such as:

Kale
Spinach
Turnip greens
Collards
Swiss chard
Parsley
Mustard greens

In addition to foods containing vitamin K, certain beverages can increase the effect of warfarin, leading to bleeding problems:

Cranberry juice
Alcohol

If you take warfarin, eat a sensible diet. Talk to your doctor before making any major changes in your diet. If you are unable to eat for several days or have persistent stomach upset, diarrhea or fever, consult your doctor. He or she may need to adjust your warfarin dose.