Monocytosis is an increase in the number of monocytes circulating in the blood.[1] Monocytes are white blood cells that give rise to macrophages and dendritic cells in the immune system.
In humans, monocytosis occurs when there is a sustained rise in monocyte counts greater than 800/mm3 to 1000/mm3.[2]
Monocytosis has sometimes been called mononucleosis,[3] but that name is usually reserved specifically for infectious mononucleosis.