I often hear many patients refer to thick blood, which is not really a medical term. Thick blood probably refers to thick blood, prone to thrombosis, or a sign before the occurrence of thrombosis, and in many cases it is also understood to be caused by an increase in blood lipid levels. Thickening is probably a medical concept of blood rheology, which is equivalent to a hypercoagulable state, related to the patient’s age and changes in blood composition, and manifests itself as an activated state of the coagulation system. The hypercoagulable state is an important risk factor for thrombosis, such as deep vein thrombosis and/or pulmonary embolism in patients with easy embolism. In addition to the hypercoagulable state of the blood, thrombosis also depends on the presence of vascular (tissue) damage and on the presence of factors that stagnate or slow blood flow, such as atherosclerotic plaque rupture leading to myocardial infarction, atrial fibrillation leading to left atrial thrombosis and cerebral embolism, so thrombosis is closely related to the presence of risk factors for thrombosis. For example, the main risk factors for cerebral embolism are valvular disease, atrial fibrillation, and post-valve replacement, and the main risk factors for myocardial infarction are hypertension, hyperlipidemia, and smoking. Clinical rheology testing (referred to as hematology) is actually an in vitro method to simulate the flow of blood in the body in order to make judgments about the coagulation status of blood and to predict future thrombosis. Even if it does, as mentioned above, thrombosis depends on a variety of risk factors, especially slowing of blood flow (sludge) and vascular injury are important initiating factors. Therefore, clinical decisions about who needs antithrombotic drugs cannot be made solely on the basis of blood rheology findings, and blood rheology factors have so far been poorly correlated with the occurrence of cardiovascular disease; moreover, blood rheology is not an observable indicator of the effectiveness of antithrombotic drug therapy. In addition, although there is a correlation between hyperlipidemia and thrombosis, increased lipids cannot be called thickening. For the prevention and treatment of thromboembolic diseases, the risk factors that may cause thromboembolism, such as hypertension, hyperlipidemia and diabetes mellitus, should be controlled or removed first, and on this basis, aspirin and other anti-thrombotic drugs should be used for a long time.