Patients who take blood thinners like Coumadin must by closely monitored by means of an “International Normalized Ratio” blood test (INR). INR tests results between 2.0 and 3.0 are generally considered as the proper “therapeutic” range for the prevention of blood clots. However, some high-risk patients require a higher “therapeutic” range between 2.5 and 3.5.
When a person is first prescribed Coumadin, they receive INR testing every several days to ascertain the dosages required to maintain the proper “therapeutic” range. Based upon several different factors, the patient may be required to take different doses of Coumadin at different times of the day until a stable therapeutic range is determined. After the patient is considered stable, they continue to require INR blood tests every 4-6 weeks.
Continued monitoring is important because changes in diet, weight, and physical activity can take a person out of their “therapeutic” range. In addition, several medications, health supplements and foods can alter the effectiveness of Coumadin.