Interference of K vitamins with oral anticoagulants. Participants were treated with acenocoumarol until they reached a stable target INR level of 2.0. Subsequently they received a daily dose of vitamin K (as indicated) for 1 week. At the end of the week blood was taken by venipuncture, and the vitamin K dose was increased during the next week. Points are means of 12 values; error bars represent SD. ○ indicates K₁; and •, MK-7.