Numerous patients (including venous diseases such as lower extremity deep vein thrombosis and postoperative Buga syndrome) are treated with long-term oral warfarin anticoagulation. At present, the efficacy of oral warfarin is relatively certain, but there is a risk of bleeding, which requires strict monitoring of the prothrombinogen international normalized ratio (PT-INR). The ideal ratio reported abroad is 2.0-3.0, but according to the national constitution we recommend a range of 1.8-2.5, i.e., a range with less risk of bleeding for anticoagulation to take effect. Warfarin dose is usually started at 2.5mg or 3mg, and the prothrombin international normalized ratio (PT-INR) is checked after 3-5 days, after which it is rechecked once a week until it is relatively stable (3 times in a row) within the target range, and a recheck of coagulation once every 2-4 weeks can be considered. After stabilization, a 4-week or longer review can be scheduled. However, there are many factors affecting the efficacy of warfarin that require careful monitoring rather than carelessness. Dose adjustment is generally in increments of 1/4 tablet, and can be adjusted by 1/2 tablet if the ratio is short of the target. If the INR is greater than 3.5, consider stopping the drug for 3 days, and then review and adjust the medication.