Background: With the discovery of vitamin K antagonists more than 50 years ago as an oral anticoagulant drug for the treatment and prevention of venous thromboembolism (VTE), the need for coagulation testing emerged. Vitamin K antagonists, such as warfarin sodium, are efficient in reducing venous and arterial thromboembolism. However, these drugs have a narrow therapeutic window. The efficacy of them is assessed by international normalized ratio (INR). The INR values should be kept between 2 and 3 throughout the course of warfarin treatment in patients with VTE. Therefore, warfarin therapy is like a sharp sword with two edges due to its narrow therapeutic window. While INR values below the targeted levels do not prevent thrombosis propagation, elevated INR values increase the risk of bleeding complications.Patients and methods: We retrospectively present 30 patients with deep vein thrombosis (DVT) and warfarin-induced bleeding. Patients were excluded if they used new direct oral anticoagulant drugs. The type of bleeding complications was classified as major and minor bleeding groups. Results: There were 14 female and 16 male patients ranging in age from 18 to 72 years. The time interval between the onset of anticoagulant treatment and the bleeding complication ranged from 4 months to 18 months. There were gastrointestinal bleeding in 2 patients, hematuria in 6 patients, epistaxis in 7 patients, and subcutaneous hematoma in 15 patients. We interrupted warfarin therapy in all patients due to bleeding complication. Vitamin K combined with fresh frozen plasma (FFP) was administered in 2 patients with gastrointestinal bleeding. Twenty eight patients with minor bleeding were treated by warfarin withdrawal alone. Conclusion: During warfarin treatment, INR values should be regularly measured and kept within targeted values to prevent possible bleeding complications and to maintain treatment with effective drug doses. Thus, patients with an INR greater than the targeted values should be closely monitored to avoid bleeding complications. In patients with minor bleeding, it is usually sufficient to stop the treatment of warfarin.