The percentage of lymphocytes refers to the proportion of the number of lymphocytes in the total white blood cell count. Because lymphocytes are white blood cells, they are involved in the body’s immune response and include both large lymphocytes and small lymphocytes, with the former accounting for about 10% and the latter for about 90%. Under normal circumstances, the percentage of lymphocytes is about 20-40%. If the percentage is elevated or low, it often indicates that there is a problem with the body’s immunity, and the diagnosis should be further clarified according to the patient’s symptoms, signs and other auxiliary tests.