This article was written by Noelle K. LoConte, M.D.

Warfarin (brand name Coumadin) is one of the most commonly used anticoagulants (meaning a medication that thins the blood). It is used in a variety of medical situations, including atrial fibrillation, blood clots and when there is an increased risk of blood clotting due to genetic predisposition. When a patient is on warfarin, they need frequent blood draws to measure blood thinness and frequent dose adjustments until they have reached a stable level of blood thinning.