What Are Monocytes?

A monocyte is a type of white blood cell which is made in the bone marrow. It is part of the immune system and works by killing micro-organisms which are harmful to the body.[1]

Which tests include this marker?

What Role Do They Play in The Body?

The main types of white blood cells found in the body are monocytes, neutrophils, basophils, eosinophils and lymphocytes. They all play a key role in defending the body against invading pathogens as well as disease. 
Monocytes can differentiate into two types of cell:

1. Dendritic cell
These types of cells are known as antigen-presenting cells. They flag cells which are foreign bodies and need to be destroyed by lymphocytes.

2. Macrophages
These are cells which phagocytose – engulf and absorb invading bacteria, small cells and bacteria. They are like neutrophils but are larger and have a longer lifespan. 

Monocytes account for up to 10% of the total white cell count. An increased monocyte count is associated with infections and inflammation. Whereas, low counts could be an indicator of severe bone marrow toxicity.[2] 

How Do Monocytes Affect My Wellbeing?

A low number of monocytes is a characteristic of some forms of leukaemia such as hairy leukaemia.[3] It may also be an effect of bone marrow injury. Low monocytes levels can also mean an increased susceptibility to infection.

A high monocyte count is found in some forms of leukaemia as well as in response to infection and inflammation. During infection, monocytes travel to the site of infection and engulf the invading pathogen. They also secrete signalling proteins called cytokine which recruit other immune cells to the site of infection to remove it from the body.[4]

How Can I Improve My Result?

You may not be able to directly influence your monocyte count but with a good lifestyle, you can improve the efficiency of your immune system.

Smoking can also damage your immune system and its response. However, some of the damage is reversible if you stop smoking.[5]


Nutrition is an important factor in our health and immune status. If we are deficient in some nutrients, then this can make our immune system weak.[6] Micronutrients including zinc, selenium, iron, copper, vitamins A, C and E, B6 and folic acid all have important influences on our immune responses. Therefore, it is essential to maintain a healthy and balanced diet incorporating all these micronutrients.[7]


Exercise is key to a healthy lifestyle. However, intense exercise can also induce immunodepression during recovery. Therefore, it is essential that you take rest periods between bouts of intense exercise to prevent illness.[8]

Tests that include this marker


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[1] PubMed Health. (2018). Monocytes. Available at:

[2] York, M, J. (2012). Chapter 8 – Clinical Pathology. In: A Comprehensive Guide to Toxicology in Preclinical Drug Development.

[3] Saeed, L., Patnaik, M, M., Begna, K, H., Al-Kali, A., Litzow, M, R., Hanson, C, A., Ketterling, R, P., Porrata, L, F., Pardanani, A., Gangat, N and Tefferi, A. (2017). Prognostic Relevance of Lymphocytopenia, Monocytopenia and Lymphocyte to Monocyte Ratio in Primary Myelodyplastic Syndromes: A Single Center Experience in 889 Patients. Blood Cancer Journal: 7. 

[4] Chiu, S and Bharat, A. (2016). Role of Monocytes and Macrophages in Regulating Immune Response Following Lung Transplantation. Curr Opin Organ Transplant: 21(3), pp 239-245.

[5] Brodin, P and Davis, M, M. (2017). Human Immune System Variation. Nature Reviews: Immunology: 17(1), pp 21-29.

[6] Kafeshani, M. (2015). Diet and Immune System. Immunopathologia Persa: 1(1).

[7] Chandra, R, K. (1997). Nutrition and the Immune System: An Introduction. American Journal of Clinical Nutrition: 66, pp 460S-463S.

[8] Peake, J, M., Neubauer, O., Walsh, N, P and Simpson, R, J. (2016). Recovery of the Immune System After Exercise. Journal of Applied Physiology: 122, pp 1077-187.

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