Definition of International normalized ratio International
normalized ratio: A system established by the World Health
Organization (WHO) and the International Committee on Thrombosis
and Hemostasis for reporting the results of blood coagulation
(clotting) tests. Abbreviated INR. Under the INR system, all
results are standardized. For example, a person taking the
anticoagulant warfarin (brand name: Coumadin) would regularly
have blood tested to measure the INR. The INR permits patients
on anticoagulants to travel and obtain comparable test results
wherever they are. Last Editorial Review: 3/19/2012 Back to
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