Diet and Warfarin


If you are undergoing treatment for cancer, your health care team will advise you about general dietary recommendations that are helpful. This may include instructions such as avoiding citrus food; spicy, acidic, or very hot food; salty items; alcohol; and tobacco. In addition to this, you may need to take some additional dietary precautions if you are taking Coumadin or Warfarin as part of your cancer treatment.

Click here for medical information on Coumadin® and warfarin.

What is warfarin?

Warfarin is an anticoagulant (blood thinner). Warfarin reduces the formation of blood clots and is used to prevent heart attacks, strokes, and blood clots in veins and arteries.

The amount of warfarin needed to manage specific health conditions varies from person to person. Your doctor will monitor your blood on a regular basis to make sure that the amount of warfarin you are taking is right for you. It is important that you do everything you can to help warfarin work properly in your body. This includes avoiding food, dietary supplements, minerals, and herbs that can interfere with how warfarin works in the body.

Warfarin and Your Diet

Vitamin K plays a role in helping blood clot in the body. Warfarin decreases blood clotting by acting on vitamin K. For this reason, you need to avoid sudden changes in the amount of vitamin K that you eat while taking warfarin. You do not need to completely avoid vitamin K while you are taking warfarin. However, it is important that you eat about the same amount of vitamin K each day. The best way to do this is to follow your normal diet and continue to eat the same foods you have always eaten.

  • While you are taking warfarin, do not make any sudden changes in the amount and type of food you normally eat without discussing it with your doctor, nurse, or dietitian first. Eat a normal, balanced diet and do not go on a weight loss diet or make other changes in your eating habits.
  • While you are taking warfarin, do not take any new or different dietary supplements, vitamins, minerals, or herbs without discussing it with your doctor, nurse, or dietitian first. These products can interfere with how warfarin works in the body and may lead to serious complications.
  • Call your doctor right away if you are unable to eat for several days or if you have stomach upset, diarrhea, or fever. If you are not eating, this will decrease the amount of vitamin K in your body and could affect how warfarin is working.

These precautions are important because the effects of warfarin depend on the amount of vitamin K in your body .

Vitamin K in Food

Foods that are rich in vitamin K include liver, other organ meats, and green and leafy vegetables such as asparagus, broccoli, cabbage, brussels sprouts, collard greens, kale, dark green lettuce, swiss chard, turnip greens, spinach, endive, okra, scallions (green spring onions), watercress, bok choy, coriander, parsley, green beans, and green peas. Food that is enriched with vitamin K, such as egg noodles, also may contain a lot of this nutrient. It is important that you do not make large changes in the amount of these foods that you eat every day while you are taking warfarin.

Remember, you do not need to avoid these foods, you just need to make sure that you do not make large changes in the amount of these foods in your diet. If you normally eat these foods, you may continue to do so.

Finally, cranberries and cranberry juice can interfere with how warfarin works in the body. Do not eat cranberries or drink cranberry juice while you are taking warfarin.

Dietary Supplements and Warfarin

Many dietary supplements contain vitamin K. Also, some herbal products and other supplements that do not contain vitamin K can affect how warfarin works in the body. For this reason, while you are taking warfarin, do not use dietary supplements without discussing it with your doctor, nurse, or dietitian first.

Dietary supplements that can interact with warfarin and lead to serious complications include:

  • Multivitamins
  • Cranberry herbal products
  • Coenzyme Q10
  • Ginseng
  • Garlic
  • Dong quai
  • Bromelain
  • Papain
  • St. John's Wort
  • Danshen
  • Gingko biloba
  • Arnica
  • Chamomile
  • Devil's Claw
  • Evening Primrose Oil
  • Fenugreek
  • Feverfew
  • Ginger
  • Horse Chestnut
  • Ipriflavone
  • Policosanol
  • Red Clover
  • White Willow
  • Alfalfa
  • Green tea supplement (drinking green tea is ok)
  • Vinpocetine
  • Passion Flower
  • Pau d'arco
  • Clove
  • Goldenseal
  • Nettle
  • Black Cohosh

Do not take any of these dietary supplements or herbal products without first talking to your doctor, nurse, or dietitian.

Final Note on Vitamin K

If you and your doctor are having a difficult time managing your dose of warfarin, you may want to ask about taking a vitamin K supplement. It may seem that taking a vitamin K supplement would be the last thing you would want to do. However, for people who have very little vitamin K in their body, getting a steady, consistent amount of vitamin K from a dietary supplement can help "even out" how the body responds to warfarin (1,2). However, do not take a vitamin K supplement without talking to your doctor first. Discuss this option with your doctor, nurse, or dietitian to determine if it is right for you.


  1. Sconce E, Avery P, Wynne H, Kamali F. Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin. Blood. 2007;109(6):2419-23.
  2. Kurnik D, Loebstein R, Rabinovitz H, Austerweil N, Halkin H, Almog S. Over-the-counter vitamin K1-containing multivitamin supplements disrupt warfarin anticoagulation in vitamin K1-depleted patients. A prospective, controlled trial. Thromb Haemost. 2004;92(5):1018-24.
This content was last reviewed August 15, 2010 by Dr. Reshma L. Mahtani.
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