Venous embolism is mainly caused by increased blood viscosity. Common causes of venous embolism include slowing down of blood flow, damage to the walls of the venous blood vessels, and hypercoagulability of the blood. 1. Slowing down of blood flow: It is common in cases of prolonged bed rest due to surgery, major chronic diseases, trauma, etc., or prolonged sitting due to long distance traveling, venous compression, advanced age, cardiorespiratory failure, etc., which can lead to slowing down of venous blood flow, thus thrombus can easily be formed and lead to venous embolism. 2. Damage to the wall of venous blood vessels: endocrine diseases such as diabetes mellitus, severe infections, inflammatory bowel disease, phlebitis, trauma, central venous catheterization, etc. can lead to damage to the wall of the venous blood vessels, which can activate the coagulation system and lead to thrombosis, resulting in venous embolism. 3. Hypercoagulable state of blood: It is common in pregnancy, long term smoking, tumor, long term use of oral contraceptives, etc. In this case, the coagulation system of the blood is over-activated, which leads to the formation of thrombus easily and thus venous embolism occurs. Venous embolism often occurs in people with family history, sedentary occupations, obese people, pregnant women, the elderly, people who have undergone major surgery, etc. It is recommended that the corresponding groups of people should consult the doctor in time to clarify the cause of the disease and actively treat it.