A substance that decreases the clotting (coagulating) ability of the blood. Sometimes called blood thinners, although they do not actually thin the blood. They do NOT dissolve existing blood clots. Commonly prescribed include: Dalteparin (fragmin), Danaparoid (Orgaran), Enoxaparin (Lovenox), Heparin (various), Tinzaparin (Innohep) and Warfarin (Coumadin).