Which vitamin is essential for the blood-clotting process?

Vitamin K is essential for the blood-clotting process. The liver uses it to activate several proteins in the coagulation system, including factors II, VII, IX, and X. Without sufficient vitamin K, these proteins cannot function properly, so bleeding may last longer or become harder to stop.

Vitamin K is a family of fat-soluble compounds rather than one single molecule. Vitamin K1, or phylloquinone, is abundant in green leafy vegetables, while vitamin K2 forms are produced by bacteria and occur in some animal and fermented foods. The letter K comes from the Danish word “koagulation.”

A common mix-up is confusing vitamin K with platelets. Platelets form an initial plug at an injured blood vessel, while vitamin K helps produce functional clotting proteins that strengthen and stabilize the clot. The anticoagulant warfarin works partly by interfering with vitamin K recycling. Vitamin K was identified through research by Henrik Dam, who shared the 1943 Nobel Prize in Physiology or Medicine with Edward Doisy.