Low lymphocyte percentage means that the percentage of lymphocytes is lower than normal. In clinical practice, the reference value for lymphocyte percentage is 20-40%, and a low lymphocyte percentage means that there is a decrease in the number of lymphocytes in the body. Lymphocytes can be categorized according to their size into small lymphocytes (6-10 um) and large lymphocytes (10-15 um), and most of the cells are oval or round in shape. Low lymphocyte percentage, or lymphopenia, is usually seen in cases of gammaglobulin deficiency, radiation injury, T-cell immunodeficiency, and with the use of alkylating agents and adrenocorticotropic hormones. When the patient has a low lymphocyte percentage, it is recommended to consult a doctor as soon as possible for treatment under the guidance of the doctor.