For people taking blood-thinning medications, it is important to make sure that the medication is working properly to avoid serious complications. To help ensure safe treatment, a healthcare provider will take a blood sample and test how long it takes the blood to clot. This amount is then compared to an average to establish your international normalized ratio (INR).
It is important that your INR levels are within normal limits. If your ratio is too high, it means it takes longer for your blood to clot and you may have an increased risk for uncontrollable bleeding. If your INR falls below the normal levels, your blood may clot too quickly and increase your risk for a stroke.
(Click INR for more details on the specific levels of INR that are considered within a normal range, as well as information on how often this ratio needs to be checked.)
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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