Excessive anticoagulation is known to raise the risk of major hemorrhage.
The report appears in the March 4 Journal of the American Medical Association . Warfarin is a blood-thinning drug taken by millions of people with a heart condition called atrial fibrillation to prevent the development of blood clots that could cause strokes. It also is taken to prevent clots around replacement heart valves and to dissolve blood clots in the legs or lungs. Too little anticoagulant effect and the patient could develop a clot that might travel to the brain and cause a stroke, too much anticoagulation and the patient could suffer a major hemorrhage. The MGH team surveyed 289 patients from the hospital's anticoagulation unit within 24 hours of a regular outpatient INR test.