If you are taking a blood-thinning medication, such as warfarin (Coumadin®, Jantoven®), you will regularly have a blood test to measure your international normalized ratio (INR). The INR value is a measurement of how long it takes your blood to clot.
By testing your INR level, your healthcare provider can make sure your dosage of blood-thinning medication is at a safe and effective amount. The higher your dosage amount, the higher your INR value. However, if your INR is too high, it can increase your risk for dangerous, uncontrollable bleeding; if your INR is too low, you may have an increased risk for a blood clot or stroke.
When first starting a blood-thinning medication, the INR value is checked two to three times per week. After your body has become accustomed to the effects of the medicine, INR testing is usually done only once or twice a month.
(For more details on this testing, click INR. This featured eMedTV article offers a complete overview of how the INR test is performed, how to interpret your results, and what factors may interfere with your value.)