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How Warfarin Interacts With Common Herbs And Supplements

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Adverse reactions after mixing pharmaceutical drugs and herbs or supplements are becoming increasingly common. Warfarin (trade name: Coumadin), one of the most frequently prescribed drugs in the United States used as a blood-thinner is one such drug that has many herbal, supplement, and food contraindications. The importance of consulting an appropriately trained health care provider before taking herbal medicine and supplements can not be overemphasized. Some of the items on this list are not absolute contraindications and can be safely taken with warfarin under professional supervision.

Herbs and supplements that could potentially reduce the effect of warfarin

  • Vitamin C
  • Ginseng 
  • Coenzyme Q10 (CoQ10)
  • St. John's wort
  • Papaya

Herbs and supplements that could potentially increase the effect of warfarin

  • Dan shen
  • Devil's claw
  • Garlic
  • Gingko biloba
  • Dong quai
  • Fenugreek
  • Vitamin E
  • White willow
  • Feverfew
  • Chuan xiong (Ligustici chuanxion)
  • Tao ren (Persicae)
  • Hong hua (Carthamus tinctorii)
  • Shui zhi (Hirudo seu whitmania)

The above is a partial list and should not replace medical consultation, as herbs and supplements are continually added to the list when new interactions are discovered.

If you are taking warfarin, call you physician immediately if you experience:

  • discomfort, pain, and swelling
  • increased bleeding from cuts or nosebleeds
  • unusual bleeding from gums when brushing teeth
  • increased menstrual flow or vaginal bleeding
  • red or dark brown urine
  • red or black stools
  • unexplained bruising
  • any other unusual symptoms

More on drug interactions.


Fugh-Berman, A. Herb-Drug Interactions. Lancet 2000; 355.

Lee Page II, Lawrence, J.D. Potentiation of Warfarin by Dong Quai. Pharmacotherapy 1999; 19 (7).

Tam L.S., Chan T.Y.K., Leung, W.K., Critchley, J.A.J.H. Warfarin Interactions with Chinese traditional medicines; danshen and methyl salicylate medicated oil. Aust NZ Journal of Medicine 1995; 25.

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