Deep Vein Thrombosis (DVT), a kind of Venous Thromboembolism (VTE), is a potentially fatal disease causing significant morbidity, mortality and expenditure. Treatment aims at preventing the thrombus extension and pulmonary embolism (PE) and decrease the incidence of recurrent VTE and post-phlebitic syndrome (PPS). Many lines of treatment were tried, however now its dealt with heparin for a week overlapping with Oral Anticoagulants (OACs) and once effects of these are established OACs are continued for 3-6 months with International Normalised Ratio (INR) monitoring. INR is roughly the ratio of the patient prothrombin time to the mean normal prothrombin time. The recommended INR for prophylaxis and treatment of thrombotic disease is 2-3. Resistance to warfarin has been described as the inability to prolong the prothrombin time or raise the INR into the therapeutic range (TTR) when the drug is given at normally prescribed doses. Warfarin resistance is very difficult to determine because it varies within population depending on individual dietary habits, metabolic status let alone the genetic makeup. Warfarin failure is also reported, defined as a new thrombotic event despite a therapeutic prothrombin time and INR. Moreover, warfarin differs from most other drugs in that the dosage required to achieve a desired therapeutic effect varies greatly among individuals, hence many patients are also unable to achieve or maintain the target desired INR.