Many patients taking warfarin do not understand or accept repeated blood draws, which affects the treatment. This is a simple explanation in the hope that patients will have more and better understanding and can better cooperate with the doctor’s treatment, so that patients can get better results. Warfarin is the most commonly used oral anticoagulant drug in clinical practice, and there is no better alternative drug. The role of Warfarin is to prevent the formation of thrombus, and to prevent the further expansion of the formed thrombus and the formation of new thrombus, and to prevent the occurrence of thromboembolism, the complications of which are often fatal in clinical practice. Patients who have undergone heart valve replacement and patients with deep vein thrombosis, as well as patients with long-term atrial fibrillation need to take Warfarin for a long time, because the role of the drug is anticoagulation (affect the clotting and hemostasis), such as overdose will lead to all kinds of bleeding, and underdose will not achieve the therapeutic effect, so know whether the amount is enough? The doctor’s basis is to draw blood tests to see the coagulation function to ensure that the medication is just right. Patient response to anticoagulants can be affected by many factors individually or in combination, including travel, diet, environment, physical condition, other diseases, and changes in medication. To monitor the patient’s responsiveness, the proper approach is for the patient to have an additional PT/INR several times when they are newly discharged from the hospital or taking other medications, discontinuing medications, or taking medications irregularly so that the medication dose can be adjusted in a timely manner. It is recommended to check PT/INR once a month, but not more than once a month. Therefore, it is recommended that patients must have their blood tests drawn in a timely manner as advised by their doctors to ensure the effectiveness of their medication.