Patients receiving long-term oral anticoagulation therapy (OAT) can monitor their own coagulation control with portable devices that measure capillary whole-blood prothrombin time (PT). The anticoagulant activity of warfarin is monitored by the prothrombin time (PT) using the International Normalized Ratio (INR). After testing, patients either notify their physicians of the results or use an individualized algorithm to adjust their warfarin dosage to maintain PT within a target zone. The goal of self-monitoring and self-management of PT is to improve anticoagulation control and reduce the frequency of adverse events.