Low absolute lymphocyte values may be caused by medical causes, congenital causes and acquired diseases. 1. Medical causes: application of adrenocorticotropic hormone, alkylating agent, anti-lymphocyte globulin and other treatments, as well as radiation therapy and other immunosuppressive and anti-tumor treatments may lead to low absolute lymphocyte values. 2. Congenital causes: hypogammaglobulinemia, congenital thymic dysplasia and other congenital diseases can lead to low lymphocytes. 3. Acquired diseases: viral infections, some bacterial infections such as tuberculosis, typhoid fever and other infectious diseases, aplastic anemia and other blood system diseases, systemic lupus erythematosus and other autoimmune diseases may lead to low lymphocytes. 4. Others: malnutrition, lack of zinc and other trace elements, long-term alcoholism and so on can lead to low lymphocytes. It is recommended that the patient should consult the doctor in time, combine the results of other clinical examinations to determine the cause of the disease, and follow the doctor’s instructions to actively treat the disease.