Low lymphocyte count is not important when other tests are normal and asymptomatic, but it is more important when there are symptoms, which are often due to pathologic factors. Lymphocytes belong to one kind of white blood cells, which have the role of defense against viral infections, and the normal value of lymphocyte count is (0.8~4)×10⁹/L. The low value is related to the following factors, including infections, malignant tumors, cirrhosis of the liver, immune system diseases and hematological system diseases: 1. bacterial infectious diseases: for example, in acute appendicitis and pancreatitis, a marked increase in neutrophils and a decrease in the number of lymphocytes may be observed. 2. Malignant tumors: cancer patients given radiotherapy or chemotherapy can lead to bone marrow suppression caused by a decrease in the number of lymphocytes. 3. Liver cirrhosis, hypersplenism: it can lead to an increase in the destruction of whole blood cells and a decrease in lymphocytes. 4. Immune system diseases: such as systemic lupus erythematosus, etc., can lead to a decrease in the number of whole blood cells, and therefore the number of lymphocytes will also decrease. Prednisone and other drugs should be given in time. 5. Hematologic diseases: such as aplastic anemia, etc., there will be a decrease in the absolute value of lymphocytes. If left untreated, it can be life-threatening due to progressive myelopoietic failure. If only the lymphocyte count is low in routine blood tests, and other results are within the normal range, and the patient has no uncomfortable symptoms, it is usually not too serious, and regular rechecks of routine blood tests will be sufficient. If the lymphocyte count is significantly low and there are symptoms such as cough, sputum, fever, abdominal pain, etc., it is necessary to pay close attention to the cause of the problem and give the cause of the disease treatment under the guidance of a physician.