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[H1] Monocytes Monocytes are a type of white blood cell and play an integral part in your immunity. Monocytes can transform into other types of immune cells when an invading pathogen enters the body, killing it or alerting the rest of the immune system before the invader can cause an infection.

Author: Leanne Edermaniger

June 20, 2024

Reviewed by: Dr Thom Phillips

In this article:

What are Monocytes?

Monocytes are a type of white blood cell and an important part of the immune system. Monocytes can destroy bacteria and other germs that enter the body and alert other white blood cells to help stop an infection from occurring.

Monocytes make up around 5% of the nucleated cells in the blood[1]. They are produced in the bone marrow where they grow and learn to protect the body from infection. When mature, monocytes enter the bloodstream and patrol the body, ready to defend against invaders.

If an invader such as bacteria enters, monocytes detect them and transform into two types of cells to help fight the infection. Those cells are:

  • Dendritic cells: a type of immune cell that requests backup from other immune cells[2]
  • Macrophages: immune cells responsible for surrounding and killing invading germs[3]

What do dendritic cells do?

Dendritic cells are known as antigen-presenting cells (APC). You can think of dendritic cells as signallers because they alert other immune cells to help clear an infection. They do this by collecting molecules from the invading pathogen called antigens and sending direct messages in the form of proteins to immune cells to make their way to the site of infection and kill the invader[4].

What do macrophages do?

Macrophages are detector cells that recognise invading bacteria and germs, then in response they engulf and destroy them, ridding the body of infection[5]. Macrophages are strategically placed throughout the body, so they can easily reach the site of an infection.

How do monocytes affect your health?

If monocyte numbers fluctuate, it could mean that there is an infection or injury present in the body. High monocyte numbers mean there is an excessive number in circulation which could be caused by chronic inflammation or infection. Sometimes increased monocyte numbers may indicate leukaemia, but not always.

Low numbers could suggest a bone marrow disorder. Bone marrow is the production site of monocytes. Low monocyte numbers may develop because of a low white blood cell count or treatments for conditions like cancer or HIV.

Why Take a Monocyte Blood Test?

Monocytes are usually screened during a full blood count where the numbers of red cells, white cells, and platelets are quantified, or as part of a white blood cell count. These tests can give clues about the presence of illness or infection.

Because monocytes are activated when an invading germ enters the body, increased numbers in circulation may indicate infection. Therefore, a monocyte blood test may help to identify illness or inflammation.

Low numbers could suggest that the bone marrow has been injured which may require further investigation. Low monocyte numbers indicate the body is at greater risk of infection.

Although we do not have any specific tests for monocytes, we offer a wide range of at-home blood test kits to give you a better understanding of your health and wellbeing.

What Are The Common Disorders That Affect Monocytes?

The conditions that affect monocyte numbers in the blood depend on whether you have a high or low monocyte count.

There are two common disorders affecting monocytes:

  • Monocytosis is a condition caused by an increased number of monocytes in the blood. It’s commonly linked to infections or chronic illness but can also be caused by autoimmune conditions, trauma, cancer, some medications, and cardiovascular disease.
  • Monocytopenia occurs when monocyte numbers are lower than expected. The main causes are reactions to chemotherapy, certain types of leukaemia, acute infectious stress, and aplastic anaemia.

What are the common symptoms of monocyte conditions?

Monocytosis doesn’t usually cause any symptoms. Instead, you may experience the symptoms of the underlying condition causing the high monocyte count.

So, you may experience the general symptoms of illness or infection, such as:

  • Fever
  • Swelling or inflammation
  • Weakness
  • Tiredness or fatigue

Monocytopenia symptoms include:

  • Frequent infections
  • Swollen lymph nodes
  • Feeling sick (nausea)
  • Being sick (vomiting)
  • Diarrhoea
  • Fever
  • Swelling, pain or discomfort

What are common treatments for monocyte conditions?

There are various causes of high or low monocyte numbers and treatment will depend on the underlying condition.

Monocytopenia treatment

Monocytopenia doesn’t usually require treatment, but if you have chronically low monocyte numbers, your doctor will likely treat the condition responsible. For example, aplastic anaemia treatments may include blood transfusions, iron chelation therapy, and infection prevention.[6]

Monocytosis treatment

High monocytes may be indicative of an infection. Therefore, it’s likely that the underlying infection will need to be treated. For example, if a bacterial infection is the cause of monocytosis, antibiotics are likely to be prescribed. If leukaemia is a cause of monocytosis, then chemotherapy or other cancer treatments may be an option.

What is the Normal Range for My Monocyte Count?

A normal monocyte count should be between 0.2 and 1.0 x 10*9/L[8]. If your monocyte count is outside of this range, it could indicate that you have an increased chance of developing monocyte-related conditions.

How to Keep Monocytes in the Healthy Range?

Monocytes are an integral part of the body’s immune system, so making healthy lifestyle choices can help to keep infections and illnesses at bay.

Choose healthy, nutritious foods

Diet is critical to the health and function of the immune system. Certain micronutrients are vital for the growth and activity of immune cells, including:

  • Vitamin C
  • Vitamin D
  • Zinc
  • Selenium
  • Iron

Most people will consume adequate amounts of these immune-boosting micronutrients, carbohydrates, proteins, and fats, by following a balanced diet. However, diets that contain lots of processed foods can negatively impact immunity. The Western Diet, renowned for its high sugar and fat content, is associated with a disturbed gut microbiome which can promote chronic inflammation and suppress the immune system.

Quit smoking

Cigarette smoking has numerous health implications, including suppressing the immune response[10]. That means that smokers are less successful at fighting disease.

Plan exercise rest periods

Exercise is key to a healthy lifestyle. However, prolonged bouts of intense exercise can cause a temporary depression of white blood cell function which may negatively impact the host’s immunity. Therefore, it is important to plan sufficient rest days to help the body recover from strenuous training sessions[11]. Doing so will also lessen the risk of injury which may compromise your immune system.

Practice good hygiene

Alongside a healthy diet and appropriate exercise, it’s also important to practice good hygiene:

  • Wash your hands thoroughly with soap and warm water after using a toilet, coughing, sneezing, blowing your nose, and before and after touching food.
  • Take steps to avoid infection like cooking meat thoroughly and practicing good hand hygiene.
  • Keep up to date with any necessary immunisations if appropriate.

Avoid stress

Stress can disrupt the immune system, leaving you susceptible to illness and infection. Some of the ways you can help include:

  • Remove yourself from stressful situations
  • Practice mindfulness and meditation
  • Keep a journal
  • Stay in touch with friends and family

Keep alcohol intake within recommended guidelines

Alcohol consumption can increase the number of monocytes in circulation[12]. Therefore, if your monocyte count is already high, it is important to keep alcohol intake within the UK Chief Medical Officer’s advice of below 14 units per week[13].

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.

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Article references

  1. Nazir, T., Taha, N., Islam, A., Abraham, S., Mahmood, A., & Mustafa, M. (2016). Monocytopenia; Induction by Vinorelbine, Cisplatin and Doxorubicin in Breast, Non-Small Cell Lung and Cervix Cancer Patients. International journal of health sciences, 10(4), 542–547.

  2. Kulasekararaj, A. et al. (2024) ‘Guidelines for the diagnosis and management of adult aplastic anaemia: A British Society for Haematology Guideline’, British Journal of Haematology, 204(3), pp. 784–804. doi:10.1111/bjh.19236.

This article was written by Leanne Edermaniger

This information has been medically reviewed by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services