Warfarin (Coumadin) interactions: Which supplements should I avoid?

Can certain medications and dietary supplements impair the effect of warfarin (Coumadin)?

- Teena / Utah

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

Answer

Yes. Several medications and dietary supplements can affect the way warfarin (Coumadin) works in your body. For example, there's evidence that vitamin E has blood-thinning effects and may increase your risk of bleeding. Tell your doctor before taking any new medications, including herbal supplements and over-the-counter remedies. Other supplements and herbal medications known to affect warfarin (Coumadin) include:

Arnica
Bilberry
Butcher's broom
Cat's claw
Dong quai
Feverfew
Forskolin
Garlic
Ginger
Ginkgo
Horse chestnut
Inositol
Licorice
Melilot (sweet clover)
Pau d'arco
Red clover
St. John's wort
Sweet woodruff
Turmeric
Willow bark
Wheatgrass

Also, you should avoid taking aspirin and frequent or high doses of acetaminophen (Tylenol, others), which can increase the effects of warfarin and cause bleeding problems. Certain antibiotics also can interfere with the effect of warfarin, so be sure to check with your doctor before starting a new antibiotic.