 Many clinical factors predispose to an excessively high INR: advanced age, abnormal liver function, decreased vitamin K intake because of poor nutrition or poor appetite, diarrhea, antibiotics, certain other concomitant medications, alcohol in binges, and perhaps changes in warfarin preparation substituting one generic preparation for another or interchanging generic with brand-name Coumadin. The most common reason for abnormally low INRs is intake of high amounts of vitamin K from green leafy vegetables, certain drug-warfarin interactions, or failure to take warfarin appropriately. 