Lymphocytosis is a condition characterized by an increased number of lymphocytes in the blood. Lymphocytes are a type of white blood cell essential for the body’s immune response. Normal lymphocyte counts vary by age and sex, but typically, an adult has an absolute lymphocyte count of 1,000 to 4,800 per microliter of blood. When this count exceeds the upper limit, lymphocytosis is diagnosed.
