Monocytes are one type of white blood cell, and they are seen when a white blood cell differential test is conducted. A high absolute monocyte count may be the result of several different factors and usually requires further testing to determine the cause.
A high absolute monocyte count can be the result of a viral infection such as mononucleosis or measles. Acute stress and autoimmune diseases may raise the level of monocytes in the differential. Parasites can also cause an increased monocyte count. In some cases, a more serious disease may be indicated, such as tuberculosis, chronic inflammatory disease or leukemia. Chronic bowel disease, heart infections and rheumatoid arthritis may be indicated if a high absolute monocyte count is noted on blood work. A bone marrow biopsy is usually performed if blood testing doesn't reveal the source of the increased monocytes.
Monocytes are made in the bone marrow of all bones. They account for approximately 1 to 10 percent of all the white blood cells found within the body. After monocytes enter the bloodstream, they eventually end up in the spleen, where they transform into macrophages. Macrophages rid the body of debris and old cells and help regulate the immune responses of the body.