Garlic and Warfarin

Garlic is used by consumers for a wide variety of health ailments and for preventative measures. From hyperlipidemia to the prevention of tick bites, data supporting garlic's use is limitless. Patients on warfarin need to exercise caution when using the raw form of garlic in its natural form or in the many dietary supplement forms.

Despite reports from the American Society of Nutrition in March 2006, that aged garlic extract appeared relatively safe, garlic is a product associated with increased risk of bleeding in individuals taking warfarin.

Garlic (Allium sativum) is thought to provide several cardiovascular benefits, such as blood pressure lowering, serum lipid lowering, and antithrombotic activity.1, 2

You should use garlic with extreme care as additional monitoring may be required and warfarin dosage adjustments may be necessary.1 However, regular ingestion of food products containing small amounts of garlic should not pose a problem.

More frequent INR testing may help you and doctor identify drug-garlic interactions more quickly than testing less often.

Patients should not start or stop any garlic-containing product without first discussing it with their doctor. A potentially dangerous influence in INR is possible. Patient responses to garlic differ and concentrations of garlic differ from one form to another.

  1. Hebel SK, ed. The review of natural products. St. Louis: Facts and Comparisons; 1999.

2    O'Hara M, Kiefer D, Farrell K et al. A review of 12 commonly used medicinal herbs. Arch Fam Med. 1998; 7:523-36