Why would you have a high monocytes blood test?

Abnormally high counts of monocytes in the blood may be the result of chronic inflammatory disease, leukemia, parasitic infection, tuberculosis or a viral infection, according to the U.S. National Library of Medicine. Monocytes are one of five white blood cells -known as 'leukocytes'- normally present in the blood.

A blood differential test reveals abnormal or immature cells and measures the proportion of each white blood type cell present in the blood; neutrophils, lymphocytes, eosinophils and basophils are the others. In healthy persons, monocytes typically comprise anywhere from 2 to 8 percent of the white blood cell count, explains the U.S. National Library of Medicine.