What is international normalized ratio?

The international normalised (UK spelling) ratio is a laboratory test that measures the amount of time it takes for blood to clot and compares it to an average. People on blood thinning drugs (such as Warfarin) would normally have this test done on a fairly regular basis. Check out http://www.heartrhythmfoundation.org/a-fib/INR_FINAL.pdf for more ino.