Patients who are given a loading dose of warfarin often reach a supratherapeutic INR level that can place a patient at risk for bleeding and prolonged hospital stay. This complication has been attributed to excessive depression of factor VII and protein C ( 2 , 5 ). As your warfarin dosage increases, your INR levels will also increase. However, it is important that the INR value is not too high, as it might cause dangerous, uncontrollable bleeding. Therapeutic monitoring of warfarin treatment requires two key elements to be undertaken if it is to be successful: the measurement of the INR and an interpretation of the result in order to advise on dosage of warfarin and when the next test should be performed. During the initial stage of treatment, INR is checked daily; intervals between tests can be lengthened if the patient manages stable therapeutic INR levels on an unchanged warfarin dose. Newer point-of-care testing is available and has increased the ease of INR testing in the outpatient setting. When you are using Warfarin and Heparin You need to test more frequently and closely monitor your INR Level because the effect of heparin on your INR Level can lead to over-estimation of the therapeutic level of your Warfarin therapy. In general, a missed dose of warfarin is reflected in the INR within about 2 to 5 days after the dose is missed. P *The author has indicated that he is on the speakers’ bureau of the Bristol-Myers Squibb (formerly DuPont Pharmaceutical) and Aventis corporations. He is also a consultant to Aventis and AstraZeneca and has received grant or research support from AstraZeneca. †The author has. Normal INR Levels. The normal range for a healthy person not using warfarin is 0.8–1.2. However, this is a dangerously low INR for a person using Warfarin. A prothrombin time (PT) is a test used to help detect and diagnose a bleeding disorder or excessive clotting disorder; the international normalized ratio (INR) is calculated from a PT result and is used to monitor how well the blood-thinning medication (anticoagulant) warfarin (Coumadin®) is working to prevent blood clots. We regularly monitor the INR of people using warfarin in order to balance the risk of excessive bleeding (when the INR is too high, meaning that the blood is too thin) against the risk of clotting or thrombosis (when the INR is too low or the blood is too thick).