Unsuspected Source of Vitamin K in Patients Treated with Anticoagulants: A Case Report

The administration of warfarin requires careful attention. Theconcurrent intake of drugs can either enhance or compete withits anticoagulant effect. Less frequently encountered are theeffects from vitamin K added to food, intake of foods with naturallyoccurring high levels of vitamin K and diets deficient in vitaminK. We report a case in which loss of anticoagulant control wascaused by a dietary supplement taken during a weight reducingdiet by a patient who was receiving warfarin following a pulmonaryembolus. A review of the literature reveals several similarcases. Amounts of vitamin K in food supplements and in foodswith large amounts of naturally occurring vitamin K are tabulatedalong with suggestions for surveillance of patients taking anticoagulants.