High d-dimer is associated with abnormal coagulation and resistance to fibrinolytic system. Symptoms are related to specific causes, including venous thrombosis, pulmonary embolism, myocardial infarction, and immune system diseases. Symptoms include pain in the lower limbs, respiratory abnormalities, myocardial ischemia, and joint pain. 1. Venous thrombosis: mainly lower extremity venous thrombosis, which will cause abnormal blood return, causing pain and discomfort in the lower extremities, accompanied by limited mobility. 2. Pulmonary embolism: mainly pulmonary artery embolism, can cause obvious respiratory conditions, such as coughing, coughing up blood, wheezing and other symptoms, serious life-threatening. 3. Myocardial infarction: it is caused by thrombosis in the coronary artery, which will cause obvious insufficient blood supply to the myocardium, resulting in squeezing pain in the anterior region of the heart, palpitations, and even coma. 4. Immune system disorders: immune system disorders in the body can also cause relevant indicators, joint pain in the areas involved in the immune system, and some of them can also be accompanied by generalized multi-system pathologies. If you find a significant increase in d-dimer, you need to consult a doctor in time for examination and standardized treatment under the guidance of the clinician.