Overview

Monocytes are a type of white blood cell that is produced by bone marrow. They are responsible for finding and cleaning up bacteria, harmful organisms and dead cells, aiding in supporting the body’s immune system.¹ Monocytosis is when there is an increase in circulating monocytes, typically as a result of infection, injury, autoimmune disease, medication and malignancies. Monocytopenia is a decrease in monocytes, commonly found in Myelodysplastic syndromes.

Monocytosis

What does it mean when monocyte levels are high?

A high monocyte count is typically linked to a long-term infection, blood disorder or autoimmune disease. If you have an autoimmune disease, the monocytes in your body may try to break down your healthy cells by mistake.  Conditions that are linked to elevated levels of monocytes include: 

• Inflammatory disorders, like inflammatory bowel disease
• Bacterial infections, such as tuberculosis, syphilis, or brucellosis 
• Leukemia and other types of cancer, such as lymphoma 
• Sarcoidosis
• Langerhans cell histiocytosis 

In some cases, your absolute monocyte count may be high because your white blood cell count is high, this can be a result of:

• Burns or injury
• Inflammation or infection
• Autoimmune disease
• Irregular thyroid
• Malnutrition 
• Medication 
• Stress

What are the symptoms of monocytosis?

An increased monocyte level typically does not cause symptoms.  If you are experiencing symptoms, it will be due to what is causing your high monocyte count.  

How is monocytosis treated?

Monocytosis itself is a symptom of an underlying condition or infection,³ so the cause of it must be treated instead.  Your doctor or healthcare provider will perform tests to determine the appropriate treatment needed. 

Monocytopenia 

What causes a low monocyte count?

A low monocyte count is typically caused by medical conditions, medication or specific injuries, like burns. This includes:

• Infection, such as adenovirus or HIV
• Blood infections, such as bacterial sepsis
• Steroid or immunoglobulin therapy use
• Cancer treatment, such as chemotherapy or radiation therapy
• Specific types of cancer, like leukaemia and lymphoma 
• Bone marrow disorders 
• Burns to the skin

What are the symptoms of monocytopenia?

Typically there are no symptoms of monocytopenia, but you may experience symptoms of what is causing your low monocyte count.  This is something that would be discussed when you visit your doctor or healthcare provider. 

What is the treatment for monocytopenia?

Monocytopenia will not be treated by itself, instead, your doctor may carry out tests to determine the cause of your low monocyte count, and provide the relevant treatment if needed.  

If you are taking medication that is lowering your monocyte count, your doctor may recommend a lower dose or change the time that you take your medication.  You must not change or stop your medication without permission from a doctor first. 

You may find that the reason for your low monocyte count is due to a lack of important vitamins that support your immune system, such as vitamins B12, C and D.² Your doctor may recommend taking vitamin supplements. 

How to improve monocyte function

Depending on the cause of your abnormal monocyte count, you may be able to improve the function of your monocytes by changing to healthier lifestyle choices.  This includes:

• Eating a healthy and balanced diet
• Regular exercise 
• Reducing or managing stress 
• Don’t smoke or drink alcohol 
• Protect yourself from infection by frequently washing your hands and avoiding contact with people who are ill

If you have an abnormal monocyte count due to a health condition or prescribed medication, it is important that you follow your doctor's orders. 

How is a monocyte count determined?

A full blood count (FBC) is one of the most common tests that are requested by doctors. It provides in-depth information about the types and amount of blood cells in your blood, which includes a monocyte count.  A full blood count also checks for:

• Red blood cells, which help carry oxygen to your organs
• Platelets, which aid in blood clotting 
• Haemoglobin, a protein that carries oxygen in the cells

If you have abnormal blood cell levels, your doctor may recommend a blood differential test.  This type of test may also be recommended if you have:

• An infection
• Autoimmune disease
• Bone marrow disorder 
• Inflammation 

Both of these tests are performed like a regular blood test. A small amount of blood will be drawn from a vein in your arm and then sent to a lab for analysis. The results will be sent to your doctor who will discuss them with you. 

Normally, monocytes make up around 2-8% of your white blood cell count.  Absolute monocyte test results can vary slightly, depending on different factors.  Normal monocyte count levels fall into these ranges:⁴ 

• Adult: 0.2-0.8 x10⁹/L
• Children (1-12 years): 0.2-1.0 x10⁹/L

These ranges can vary depending on the healthcare system and you may be presented with a slightly different reference range by the lab that carried out your test. It is normal for men to have a higher monocyte count than women. 

Summary

Monocytes are a type of white blood cell produced in bone marrow. Their role in the body is to find and engulf bacteria and damaged cells, which is beneficial to the immune system. You may have an abnormally high amount of monocytes in your bloodstream, known as monocytosis. This is typically a result of infection, inflammation, injury or autoimmune disease. An abnormally low amount of monocytes in your bloodstream is called monocytopenia and can be a result of stress, medication, infection, or cancer in some cases. 

Monocytosis and monocytopenia are symptoms of another condition and therefore require the cause to be treated. Your doctor will ask questions and may request further tests to determine the cause of your abnormal monocyte count so that they can provide the appropriate treatment. However, in some cases, it is possible to improve the function of monocytes by making lifestyle changes, such as eating healthy, exercising frequently and cutting down or quitting the use of nicotine and alcohol. 

A monocyte count is measured with a full blood count, which provides information on the types and number of different blood cells in your body. This is performed by a simple blood test. The normal monocyte range for adults is 0.2-0.8 x10⁹/L. It is important to note that blood count ranges can vary depending on age, gender, location, and healthcare services.