Which drug is an oral anticoagulant that requires keeping vitamin K intake consistent?

• A. Warfarin
• B. Heparin
• C. Dabigatran
• D. Rivaroxaban

Answer: (A)

The key idea is that some anticoagulants are affected by vitamin K in the diet. Warfarin is a vitamin K antagonist, meaning it blocks the recycling of vitamin K and reduces activation of several clotting factors. Because of this, the amount of vitamin K you consume can shift how strongly warfarin acts. If vitamin K intake varies a lot, the anticoagulant effect can swing, leading to either too much bleeding or too little prevention of clots. Therefore, keeping vitamin K intake consistent—rather than eliminating it—helps maintain stable anticoagulation, with regular INR monitoring guiding dose adjustments.

In contrast, the direct oral anticoagulants and heparin work through mechanisms that aren’t driven by vitamin K in the diet, so their effect isn’t tied to how much vitamin K you eat.