A laboratory blood test called the international normalized ratio (INR) is used for people who are taking blood-thinning medications, such as warfarin (Coumadin®, Jantoven®). The INR value measures how long it takes for the blood to clot.
A healthy person who is not taking a blood-thinning medicine will typically have an INR of about 1. However, people taking oral blood-thinning medicines have a higher INR value. As the dose is increased, a person's INR should also increase.
If the INR is out of range, it could lead to potentially serious complications. For example, if a person's INR is too high, it can lead to uncontrollable bleeding; an INR that is too low may increase your risk for a stroke.
(For more information, click INR. This full-length article provides detailed information on how the INR value is calculated, how often this test is performed, and the specific values that are considered an ideal INR range.)
Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: ArthurSchoenstadt, MD
List of references (click here):
Zehnder JL. Drugs used in disorders of coagulation. In Katzung BG, editor. Basic and clinical pharmacology. 10th ed. 2007, New York (NY): McGraw-Hill; 2007. Pg. 551.
Haines ST, Witt DM, Nutescu EA. Venous Thromboembolism. In DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, editors. Pharmacotherapy: A Pathophysiologic Approach. 7th ed. New York (NY): McGraw-Hill; 2008. Pg. 331-370.
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