High dimer is a common clinical test for elevated D-dimer, a sensitive but non-specific marker of acute thrombosis. An elevated value indicates the presence of thrombosis. Elevated D-dimer reflects the presence of important molecular markers of increased coagulation and fibrinolytic activity in the body and is usually tested together with the five coagulation tests. The human blood flows normally and relies on the dynamic balance of fibrinolytic enzymes and trypsin in the blood. When a patient has vascular damage, a thrombus is formed and the D-dimer is detected in the blood and is elevated. Its elevation is only one indicator, and other tests are needed to confirm the diagnosis of a disease. As long as there is activated thrombus formation and fibrinolytic activity in the body’s blood vessels, D-dimer will be elevated. This can easily trigger some thrombotic diseases, such as myocardial infarction, cerebral infarction, lower extremity venous thrombosis, tumors, and diffuse intravascular coagulation. The most common ones are cardiovascular diseases, namely myocardial infarction and cerebral thrombosis. Therefore, the elevation of D-dimer still needs to be given some attention. Therefore, since D-dimer is not a non-specific indicator, it needs to be combined with other tests when diagnosing the disease in clinical practice.