If you are taking certain blood-thinning medications, such as warfarin (Coumadin®, Jantoven®), you will have frequent blood tests to make sure you are not at risk for developing serious problems. The international normalized ratio (INR) is a laboratory test used to calculate how long it takes your blood to clot.
If you have an elevated INR, it means that it takes a long time for your blood to clot. This can help prevent blood clots. However, if your INR is too high, it may lead to uncontrollable bleeding.
(Click INR for more details on what may happen if your INR is elevated. This full-length article also explains the potential risks of having an INR that is too low.)