There are two forms of natural vitamin K, phylloquinone and menaquinone. Phylloquinone, vitamin K1, is the major type of dietary vitamin K, which is present in high amounts in green vegetables, while menaquinone, vitamin K2, is synthesized by the human intestinal bacteria. Furthermore, a synthetic type of vitamin K is known: vitamins K3. Vitamin K-dependent proteins require carboxylation of certain glutamate residues for their biological functions such as blood coagulation (factor II, VII, IX, X and proteins C, S and Z), bone metabolism (osteocalcin) and vascular biology. Without vitamin K, blood coagulation is impaired, and uncontrolled bleeding occurs. Low levels of vitamin K also weaken bones and promote calcification of arteries. The aim of this study is to examine how genetic variations influence responses to oral anticoagulant therapy. There is a large variability in response to anticoagulant therapy, and this can modify the benefit/risk ratio of drugs. This variability can be explained by clinical factors such as age, sex, demographic and environmental factors, inter- and intra-individual variability and genetic variants. In recent years, several genetic polymorphisms have been associated with variable biological responses to oral anticoagulants.