What Are the Causes of High Monocyte Levels?

Monocyte levels higher than 8 percent are considered elevated, which can be caused due to inflammation, virus-related fever, stress or organ necrosis. Monocytes are one type of white blood cell measured during a blood differential test, notes the National Institutes of Health’s Medline Plus.

Normal levels of monocytes in the blood range from 2 to 8 percent. An elevated level of monocytes, also known as monocytosis, is often a sign of many different types of inflammatory or autoimmune disorders, blood disorders and cancer, as well as high stress levels. Monocytosis is also linked to parasitic infections, tuberculosis, mononucleosis, mumps and measles.

Monocytes help clean up the body’s dead or damaged tissue. In a healthy person, monocytes should account for 1 to 10 percent of circulating leukocytes, as noted by Merck Manuals. Monocytes circulate in the bloodstream for a few hours, then move to organs, such as the spleen, liver, lungs, wound sites and bone marrow where they become macrophages. Once there, they break down debris, cancer cells and any foreign substances in a process knows as phagocytosis.

In some cases, higher levels of monocytes can cause decreased levels of other white blood cell types, such as neutrophils, lymphocytes, eosinophils, basophils and young neutrophils. If a high number of monocytes are present in the blood, physicians will take into account medical history, perform tests and evaluate symptoms to make a diagnosis.