Dietary vitamin K intake and anticoagulation control during the initiation phase of warfarin therapy: A prospective cohort study

Dietary vitamin K influences warfarin response, but its effect on anticoagulation control during the initiation phase of therapy is still poorly quantified. Studies of patients already on stable warfarin therapy have shown that lower mean daily vitamin K intake is associated with unstable and non-therapeutic International Normalised Ratios (INRs) (1, 2), and higher vitamin K intake may lead to sub-therapeutic INRs (3). The risk of adverse bleeding and thromboembolic events, however, is greatest during the initiation phase of warfarin therapy when INRs tend to be non-therapeutic (4). In this prospective cohort study, we evaluated dietary vitamin K intake as a risk factor for poor therapeutic INR control during the initiation phase of warfarin therapy.