Heparin is a highly sulfated polysaccharide primarily used as an anticoagulant, which works mainly by inhibiting thrombin (FIIa) and/or factor Xa (FXa). It is commonly used to prevent and treat thromboembolic conditions such as deep vein thrombosis and pulmonary embolism. It also plays roles in inflammation, angiogenesis, and growth factor signaling, with potential therapeutic applications in cancer treatment and allergic conditions.