Lymphocytes are the immune cells in the body and are responsible for the body’s defense. If there is a foreign body invasion in the body, lymphocytes will increase, gather and appear to have a high absolute value of lymphocytes, which, when gathered, can destroy the foreign body and drive it away from the body. Therefore, lymphocyte increase is common in infections, inflammation or tumors, etc. If the percentage or absolute value of lymphocytes severely exceeds the normal value, be alert to lymphocytic leukemia. There is an extensive abnormal proliferation of leukemic cells in the bone marrow and other hematopoietic tissues, mainly immature lymphocytes infiltrating other tissues and organs, leading to failure of normal hematopoietic function, which is manifested by a significant decrease in normal hematopoietic cells. Therefore, if the lymphocyte percentage is found to be only slightly high and one does not have any other symptoms, one should not bother about it because one’s own immunity may wipe out the virus. However, if there is a high absolute lymphocyte percentage, it is recommended to do specific tests to exclude inflammation, tumors.