Vitamin K (the name is derived from the German word koagulieren - to coagulate) is necessary for the blood clotting mechanism in the body. It thus aids in the healing of capillaries or blood vessels that may have enlarged or burst, creating the thin red lines that can often show through the skin.

Vitamin K deficiency causes hypoprothrombinemia and a fall in the concentration of the other vitamin K-dependent coagulation factors, manifested by defective coagulation and hemorrhage.

Vitamin K deficiency can occur in adults with marginal dietary intake if they undergo trauma, extensive surgery, or long-term parenteral nutrition with or without treatment with broad-spectrum antibiotics. Persons with biliary obstruction, malabsorption, or parenchymal liver disease also have a higher risk of vitamin K deficiency.