Which supplement is described as a Coumadin antidote and increases clotting?

• A. Vitamin E
• B. Vitamin K
• C. Grapefruit
• D. Vitamin C

Answer: (A)

When warfarin (Coumadin) is used, reversing its anticoagulant effect is achieved by replenishing vitamin K–dependent clotting factors. Warfarin blocks the enzyme that regenerates active vitamin K, reducing factors II, VII, IX, and X. Giving vitamin K allows those factors to be produced again, increasing clotting and reversing the anticoagulation effect. This makes vitamin K the correct choice as the antidote.

Vitamin E, by contrast, can affect coagulation by inhibiting platelet function and may actually increase bleeding risk rather than reverse it. Grapefruit doesn’t reverse warfarin’s effects, though it can interact with drug metabolism in some cases. Vitamin C has no role in reversing anticoagulation.