RESUMO
Vitamin K is a cofactor for the synthesis of blood coagulation Factors II, VII, IX and X, and inhibitors such as Protein C and S and bone matrix protein. Its active form is a coenzyme in the glutamic acid carboxylation. Vitamin K-dependent factors form enzymatic complexes with calcium and membrane phospholipids. The insufficiency of gamma glutamic carboxylation impairs the hemostatic function. Hereditary deficiencies, antibiotics and oral anticoagulants, decrease the capacity of complex formation giving way to hemorrhage or thrombosis, or bone mass disturbances which are easily treated with administration of Vitamin K. The main causes of Vitamin K deficiency are lack of hepatic storage in newborns, liver insufficiency, malabsorption, dietetic deficiency, therapy with the antibiotics and coumarin administration. For the study of Vitamin K there are methods to measure the Vit K dependent proteins and as well methods to measure specifically the quinonas.