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Food and Supplement Interactions

Food Interactions


FoodEffect on INRRecommendations/Comments
Alcohol    > ↓↑Increases INR with binging, decreases INR with chronic use
Cranberry>0There is NO significant interaction (see FAQs for more info)
Ensure/Boost   >↓Contains ~25% of daily vitamin K and usually only significant if consuming several servings per day
Goose Liver>↓Avoid due to unpredictable influence of vitamin K2
Grapefruit Juice>0No significant interaction
Green Tea>↓May lower INR in large (i.e. >1 gallon/day) quantities
Liver Meats>↓OK to eat, but treat like a vitamin K food
Mango>↑Avoid consumption of all foods containing mango as the nature of the interaction is unclear and is variable from patient to patient.
Nopales (Cactus)              >↓ OK to eat, but treat like a high vitamin K food
Soy ProductsOK to eat, but treat like a vitamin K food


Supplement Interactions


SupplementEffect on INRRecommendations/Comments
CoQ10>↓Structurally similar to Vitamin K and therefore may need modest warfarin dose adjustment: Check INR within 2 weeks of starting supplement
Dong Quai>↑Coumarin derivative
Flaxseed>↓May impair absorption of warfarin--separate administration
Kava Kava>↑
Psyllium/Fiber>↓May impair absorption of warfarin--separate administration
Red Yeast Rice>↑ 
St Johns Wort>↓ 
Vitamin E >↑ 
Vitamin KBe consistent with supplements and multivitamins containing vitamin K


Increased Risk of Bleeding due to Antiplatelet Effect

  • Feverfew
  • Fish Oil/Omega 3 Fatty Acids
  • Garlic
  • Ginger
  • Ginkgo
  • Turmeric/Curcumin

Warning in Coumadin Package Insert:

Exercise caution when botanical (herbal) products are taken concomitantly with COUMADIN. Few adequate, well-controlled studies evaluating the potential for metabolic and/or pharmacologic interactions between botanicals and COUMADIN exist.

Due to a lack of manufacturing standardization with botanical medicinal preparations, the amount of active ingredients may vary. This could further confound the ability to assess potential interactions and effects on anticoagulation.

Monitor the patient's response with additional INR determinations when initiating or discontinuing any botanicals.