Types of Vitamin K

Three forms of vitamin K are known to humans as follows:

    K1: Phylloquinone: It is the 'plant' form and is found in green leafy vegetables, vegetable oils, and dairy products. This is the form given to newborns as water soluble IM injection at birth.

    K2: Menaquinone: It is the form manufactured by bacteria in the intestines.

    K3: Menadione: This is artificially designed vitamin K that is not used any more because of its adverse effects (hemolysis).

Vitamin K is required for gamma carboxylation of GLU residues on coagulation factors (Factors II, VII, IX, and X are called vitamin K dependent factors). In absence of vitamin K abnormal/defunct proteins called PIVKAs (proteins induced by vitamin K absence) are formed. These cannot participate in the coagulation cascade leading to failure of clotting and bleeding.