The absolute lymphocyte value of 3.9 means that the number of lymphocytes is 3.9 x 10^9/L, which is above the normal range (normal range is 1.5 to 3.3 x 10^9/L), and the severity of the condition needs to be determined according to the cause of the disease. If it is a viral infection such as rubella it is usually not very serious, if it is a blood system disease such as leukemia it is more serious. Lymphocyte is a kind of immune cell, when there are infectious diseases, especially viral infections such as rubella, chicken pox, mumps, etc., because the viruses invade the body can cause the body’s immune response, resulting in an increase in the number of lymphocytes, and the condition is relatively not very serious. After standardized treatment, the number can return to normal. Blood system diseases such as leukemia and serious lymphocyte diseases such as lymphoma will also increase the number of lymphocytes, and the condition is more serious. The disease is prone to relapse and requires standardized treatment, regular checkups and follow-ups. Lymphocytosis may also be caused by other reasons, such as rejection after transplantation and tuberculosis. When lymphocyte count increase is found, the cause should be actively identified and standardized treatment should be carried out to avoid delaying the disease and causing its aggravation.