The international normalized ratio (INR) blood test helps healthcare providers ensure that your dosage of a blood-thinning medication is safe and effective.
The INR value is established by measuring the time it takes the blood to clot and then comparing it to an average.
A healthy person who is not taking a blood-thinning medicine will typically have an INR of about 1 (the ideal range is from 0.8 to 1.2). However, people taking oral blood-thinning medicines, like
warfarin (
Coumadin®,
Jantoven®), generally have a higher INR value. As the dose is increased, a person's INR should also increase.
It is important that the INR falls within a desirable range. If it is too high or too low, it could cause blood clots or uncontrollable bleeding. The desired ranges are based on a person's reason for taking the medication and include:
- 2 to 3 -- the typical range for most "blood-thinning" needs
- 2.5 to 3 -- the desired range for people who have a high risk of developing a blood clot.
(Click INR for more details on the desirable ranges of INR, as well as information on how often this test is performed.)