BackgroundWarfarin is a widely used oral anticoagulant in clinical practice. It is used to prevent arterial emboli in patients with atrial fibrillation, or prevent and treat venous thromboembolism. The efficacy and safety of warfarin depends on maintaining the INR within the therapeutic range. The proportion of time spent in the therapeutic INR range (TTR) is used to evaluate quality of anticoagulation control.MethodsA hospital-based cross sectional study was conducted between November 1, 2019 and October 31, 2020 at Cardiac and Hematology Clinic, University of Gondar hospital. A consecutive sampling method was used to recruit 338 study subjects. Proportion of time spent in the therapeutic range (TTR) was calculated using the Rosendaal’s linear interpolation method. TTR ≥65% was described as ‘optimal’ International Normalized Ratio (INR) control. The Data were entered into EPI Info version 4.4.1 and transported to SPSS version 20 for analysis. Logistic regression analysis was used to identify associated factors with optimal anticoagulation outcome (TTR ≥65%). P-values