What is Warfarin and what is an INR

What is Warfarin and what is an INR

Warfarin is a medication that decreases the body’s ability to form clots, which can affect bleeding, but it does not entirely stop clotting. Sometimes the effect of Warfarin is referred to as anticoagulation. The administration of Warfarin requires monitoring by periodic blood draws so that a healthy balance of clotting is maintained.

Blood clotting or coagulation is an important process that prevents major bleeding from an injury to a blood vessel . First the platelet forms a plug at the site of injury (primary hemostasis). Then the clotting cascade is activated which involves proteins which contribute to blood clotting. Warfarin inhibits the action of Vitamin K producing some of the clotting proteins in the liver.

The international normalized ratio (INR) measures how much time it takes to form a clot. If the level is too low, It puts the individual at risk for a blood clot. If the level is too high, it puts the individual at risk for excessive bleeding.


Kathy Valusek, DNP,MPH
Certified Nurse Practitioner
Clinical Manager -IHLC

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