Different natural (phylloquinone and menaquinone) and synthetic (menadione) compounds carry out the same action of Vitamin K in the human body. Vitamin K is a substrate for the enzyme catalysing the posttranslational conversion of specific glutamyl residues to gamma-carboxyglutamyl residues in certain proteins connected with the coagulation (Factors II, VII, IX, X), the anticoagulation (Proteins C and S) and other organic functions (osteocalcin). Foods rich in Vitamin K (1/4) and the action of gut bacteria (3/4) can give rise to changes in Vitamin K status. Dietary factors, alterations of gut bacteria or/and troubles in the absorption of this vitamin can cause a lack, which at first interferes in the normal hemostatic function and later on it leads to modifications in the bone structure. Therefore, it is necessary to pay a lot of attention to dietary intake, adequacy, bioavailability, absorption and metabolism of Vitamin K and compounds with an action similar to it for understanding the signs of lack, choosing the most suitable therapy and managing accurately the coumarin-based oral anticoagulants.