The normal range of D-dimer is <0.5mg/L, and generally the elevation of its index is of clinical significance. There are many reasons for the increase of D-dimer, such as hypercoagulable state of blood, secondary hyperfibrinolytic function, and so on. 1. Hypercoagulable state of blood: when renal disease leads to the change of coagulation factors in the body, it can lead to the increase of blood viscosity in the human body, which will lead to the increase of D-dimer index. 2. Secondary hyperfibrinolytic function: D dimer is the product of fibrin degradation, the patient’s initial coagulation function is enhanced, which will cause a large amount of fibrin production in the body. It is mostly seen in people suffering from atherosclerosis, myocardial infarction, cerebral infarction, venous thrombosis and many other thrombotic diseases. D-dimer is mainly used for the diagnosis of thrombosis in clinical practice, but the range of elevation cannot determine the severity of the disease. If abnormal indicators are found, it is recommended to consult a doctor for further examination and actively cooperate with the doctor for treatment.