INR stands for International Normalized Ratio. It is a system that has been established by the World Health Organization (WHO) and the International Committee on Thrombosis and Hemostasis for reporting the results of blood coagulation (clotting) tests. It is used for monitoring the dose of warfarin that is required to keep the blood thin enough so that it does not clot. INR of less than 1 means you are prone to clotting and if it is high (over 3.5) it means you are prone to bleeding. It is usually maintained between 2 to 3.