The number of monocytes, which are a type of white blood cell, in the blood often increases in response to an infection in the body. These cells work with other leukocytes to remove the tissue damaged by infection, according to the Merck Manual. After a few hours in the bloodstream, they move to other tissue to become macrophages. Viral infections are the most common reason for a monocyte count increase.
To check the white blood cell count, a medical provider performs a blood draw. Most of the time, a sample of blood is then placed in a machine that returns the percentage of each type of white blood cell. MedlinePlus reports the normal monocyte count as between 2 percent and 8 percent. Acute stress or infection in the body increases the percentage of one or more types of white blood cells. Increasing the percentage of monocytes reduces the percentage of other white blood cells.
An increase in monocytes sometimes indicates a parasitic infection, such as a tick bite, intestinal worm or malaria. It is common in individuals suffering chronic inflammatory diseases including arthritis. Individuals with leukemia, lymphoma or multiple myeloma also exhibit a higher than normal monocyte count, according to Family Practice Notebook.