INR also stands for the International Normalised Ratio, an international standard for measuring blood coagulability and maintaining comparisons across laboratories.
An INR of 1.0 is the defined normal INR.
Patients on long term warfarin treatment need to have their INR level checked regularly. An INR of between 2.0 and 3.0 is the target for DVT prophylaxis and an INR of between 2.5 to 3.5 is the recommended for patients with artificial heart valves.
INRs above 10.0 lead to spontaneous bleeding from mucosal surfaces - not a good thing.