A healthy person who is not taking a blood-thinning medicine will have a normal INR (international normalized ratio) of about 1. However, someone who is taking an oral blood-thinning medication typically has a higher INR value. As the dose of the medicine is increased, the INR should also increase.
The higher the INR, the longer it takes the blood to clot. This can help prevent blood clots that may lead to strokes, but it can cause uncontrolled bleeding if the ratio is too high. If the INR is too low, it may cause a blood clot and lead to a stroke.
(For more information on normal levels of this ratio, click INR. This full-length article explains in detail how the INR is calculated, how often the test needs to be done, and lists specific values for normal levels.)