What are the risks of taking anticoagulants?

Mainly Bleeding: Anticoagulants, also know as blood thinners, can cause bleeding. A cut can bleed more than usual, a bruise can lead to swelling (hematoma) as blood collects under the skin, gums or the nose can bleed, etc. Rarely, you may have an allergic reaction and a very rare problem with coumadin (warfarin) is "skin necrosis" where the med actually triggers excess clotting and injury to skin and other tissue.