Low molecular heparin has anticoagulant and antithrombotic effects and is used for the prevention and treatment of thromboembolic diseases. Low molecular heparin is used for the prevention of thrombosis and treatment of thromboembolic diseases, such as pulmonary embolism and deep vein thrombosis, by combining with antithrombin III, enhancing the affinity between antithrombin III and coagulation factor Xa, and exerting the effect of anticoagulation factor Xa to achieve anticoagulant and antithrombotic effects. Compared with ordinary heparin, low molecular heparin has the advantages of good absorption, high bioavailability, and relatively small risk of bleeding, so it is more commonly used in clinical practice. The use of low molecular heparin may have side effects such as risk of bleeding, causing thrombocytopenia, skin purpura, erythema and even necrosis at the injection site. Low molecular heparin needs to be used under the guidance of a medical professional and self-administration should be avoided to avoid adverse events such as bleeding.