Which vitamin is essential for blood clotting?

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

Answer: (D)

Blood clotting relies on certain clotting factors that must be activated through a process called gamma-carboxylation, which requires vitamin K. This modification lets these factors bind calcium and participate effectively in forming a clot. Without enough vitamin K, those factors can’t function properly, leading to delayed or impaired clot formation and a higher risk of bleeding. Vitamin K comes from leafy greens and from gut bacteria, and it’s fat-soluble. Newborns are often given a vitamin K shot to prevent bleeding problems, and some medicines (like warfarin) work by blocking vitamin K’s activity to reduce clotting. Other vitamins don’t play this direct role in activating the clotting factors, so vitamin K is the one essential for blood clotting.