Chlorella and Warfarin

Chlorella, a freshwater green algae is used as a food supplement and many claim that it can be used for cancer prevention, increasing white blood cell counts, digestion, detoxification, colitis, stress related ulcers among other things.1

Patients who take warfarin should pay special attention to chlorella because of the high vitamin K content. Chlorella may inhibit the anticoagulant effect of warfarin.2, 3 

The FDA has not evaluated the safe use of chlorella in patients taking warfarin. Patients are encouraged to discuss any use of chlorella before ingestion. A potential significant reduction in INR may be expected.

  1. Andre, C.A.. A review of recent clinical trials of the nutritional supplement Chlorella pyrenoidosa in the treatment of fibromyalgia, hypertension, and ulcerative colitis. Altern Ther Health Med. 2001 May-Jun;7(3):79-91.
  2. Ohkawa S, Yoneda Y, Ohsumi Y, Tabuchi M. Rinsho Shinkeigaku. Warfarin therapy and chlorella [Article in Japanese]. 1995 Jul;35(7):806-7.
  3. Price, A. The American Pharmaceutical Association Practical Guide to Natural Medicines. The Stonesong Press. 1999.