An absolute lymphocyte value of 3.99 x 10⁹/L is considered high and needs to be determined based on what is causing it to be elevated. The normal range of absolute lymphocyte value is (0.8~3.5)×10⁹/L, and exceeding this range indicates that it is on the high side. It can be caused by physiological factors or pathological factors, physiological high is normal, pathological high is not normal, should actively treat the primary disease. 1. Physiological high: During the period of 4-6 days to 4-6 years of age during the development of children, lymphocytes often increase physiologically. At this time, the absolute lymphocyte value of 3.99×10⁹/L is normal, and no special treatment is needed. 2. Pathologically high lymphocytes: it often suggests that there may be viral infections or neoplastic diseases, which should be further examined. (1) Viral infection: high lymphocytes are commonly found in measles, rubella, chickenpox and other viral infections. (2) Neoplastic diseases: Commonly found in acute and chronic lymphocytic leukemia, lymphoma, etc. When the absolute value of lymphocytes is 3.99×10⁹/L, the patient should do the next examination under the guidance of the doctor to clarify whether it is a normal situation. If it is diagnosed as an abnormal situation, it should be actively treated under the guidance of the physician.