Venous thromboembolism, including deep vein thrombosis and pulmonary embolism, is highly prevalent, with approximately 300,000 to 600,000 new cases per year in the U.S. Patients with VTE have a high rate of recurrent thromboembolic events, which can exceed 20-25% at 5 years, and anticoagulation is the primary treatment for VTE. For patients with long-term anticoagulation, the risk of severe bleeding may be higher than 3%. Therefore, the choice of anticoagulant and duration of anticoagulation should be carefully considered in secondary prevention of VTE. How should venous thromboembolism be prevented and treated? 1. Anticoagulants should be given to prevent VTE in hospitalized patients with cancer if there is no bleeding or other contraindications to anticoagulation. 2. Do ambulatory cancer patients need anticoagulants to prevent VTE during systemic chemotherapy? (1) Routine application of anticoagulants to prevent VTE is not recommended. (2) Patients receiving sildenafil or lenalidomide chemotherapy drugs or glucocorticoids are at higher risk of thrombosis and should be given anticoagulant therapy to prevent thrombosis. anticoagulant therapy should be given to prevent VTE. Based on current evidence, LMWH or INR-adjusted warfarin is recommended for oncology patients receiving both sildenafil and chemotherapeutic agents. 3. Should anticoagulation be given perioperatively to prevent VTE in cancer patients undergoing surgery? (1) All patients undergoing malignancy-related surgery should be given thromboembolic prophylaxis. (2) Patients undergoing laparoscopic surgery, laparoscopy, or open chest for more than 30 minutes should receive low-dose plain heparin or LMWH unless the patient has active bleeding or is at high risk for bleeding. (3) Anticoagulation therapy should be given preoperatively or administered as early as possible postoperatively. (4) Non-pharmacologic therapy can be used as an adjunct to pharmacologic therapy, but non-pharmacologic means alone should be used to prevent VTE only if the patient has a contraindication to anticoagulation due to active bleeding. (5) Combining non-pharmacologic approaches with pharmacologic therapy can be more effective in preventing VTE, especially for high-risk patients. (6) The application of postoperative anticoagulants should be continued for at least 7-10 days. Anticoagulation should be extended to 4 weeks in high-risk patients with residual postoperative lesions, obesity, or previous history of VTE who undergo major abdominal or pelvic surgery. 4.How to anticoagulate? The main method of anticoagulation is oral anticoagulation tablets. The commonly used anticoagulant is Warfarin, and oral anticoagulation tablets are usually administered after the drainage tube is removed after surgery or 48 hours after surgery as prescribed by the doctor. In order to ensure the accuracy of drug application, daily morning blood sampling for prothrombin time and activity is required during the first week after surgery. Later, the check-ups will be performed 2-3 times a week and gradually extended to once a month or once a month in February. Keep the prothrombin time at 18-24 seconds, activity at about 30%, and international standard ratio at 1.5-2.0. 5.How to observe anticoagulant overdose? Patients should always observe whether there is hematuria, nose or gum bleeding and skin bleeding spots, etc. Once these phenomena occur, they should contact the doctor immediately.