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Monocytes are a type of white blood cell in your immune system. Monocytes turn into macrophage or dendritic cells when a germ enters your body. The cells either kill the invader or alert other blood cells to help destroy it and prevent infection. High or low monocyte counts may be a sign of a condition that a healthcare provider needs to diagnose.
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Monocytes are a type of white blood cell (leukocyte) in your blood and tissues. As essential fighters in your immune system, monocytes find and destroy germs (viruses, bacteria, fungi and protozoa) and eliminate infected cells. Monocytes also call on other white blood cells to help treat injury and prevent infection.
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Monocytes are like your cell’s firefighters. Their life cycle begins in your bone marrow (soft spongy tissue inside of your bones), where they grow and train to protect your body. Once they mature, monocytes enter your bloodstream and tissues to defend your body against invaders, like germs.
Germs are similar to fires when they enter your body. Once germs are inside your tissues, monocytes hear an alarm, calling them into action to fight the fire. In order to fight, your monocytes differentiate into two types of cells:
Dendritic cells are like your fire department’s call center. They’re responsible for alerting other cells in your body to help fight infection. Dendritic cells are in superficial tissues, such as just beneath your skin and in the lining of your nose, lungs, stomach and intestines.
When a germ enters your body’s tissues, dendritic cells collect the antigen of the invading germ. An antigen is essentially a “marker” on a germ that lets your immune system know it doesn’t belong in your body. It triggers your immune system to produce antibodies against it. Then, dendritic cells release proteins (cytokines) that notify other white blood cells to come to the site of the infection and destroy the invader.
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Macrophages are on the front lines, fighting germs (viruses, bacteria, fungi and protozoa) that enter your body. Macrophage cells surround the invading germ and ingest and kill it with toxic enzymes. These cells also help remove dead cells from your tissues and bloodstream.
Monocytes are the largest type of white blood cell and are nearly twice the size of a red blood cell. Under a microscope, monocytes are easy to identify based on their size. Monocyte cells have a two-bodied nucleus (bilobed nuclei) center that floats in a contained fluid called cytoplasm.
The nucleus changes shape as the monocyte moves throughout your body. It can take the shape of:
Monocytes form in the soft tissue inside your bones (bone marrow). After the cells mature, they travel to your tissues, where they defend your body from infection alongside other cells in your immune system.
A normal monocyte count is between 2% and 8% of your white blood cell count. This equals about 200 to 800 monocytes per microliter of blood in healthy adults. But this range can vary depending on the laboratory that’s counting your monocytes. Your healthcare provider will work to identify the underlying cause if your monocytes are high or low.
Conditions vary based on the number of monocytes in your blood. Your monocyte count can be too high or too low from your body fighting an infection or disease. Sometimes, abnormal monocyte counts are a treatment or medication side effect.
A high monocyte count (monocytosis) is a potential sign of many different conditions. It’s often linked to infectious diseases, like mononucleosis, or an autoimmune disease, like lupus. Causes of high monocytes include:
Monocytopenia is when your monocyte levels are low. Anything that decreases your overall white blood cell count can cause low monocytes. Causes of low monocytes include:
A blood test checks the health of your monocytes. Two tests specifically identify how many monocyte cells are in your body:
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If you have a low or high monocyte count, you likely won’t experience any symptoms from the count itself. Instead, any symptoms you might feel are a side effect of a disorder that caused your monocyte count to be abnormal.
Treatment depends on your diagnosis and the severity of your condition. It could be as simple as changing the foods you eat or as significant as treating an underlying condition with chemotherapy. Your healthcare provider will suggest treatments specific to your diagnosis to help you choose the best way to increase or decrease your monocyte count.
Treatment to decrease your monocyte count includes:
Treatment to increase your monocyte count includes:
You can keep your monocyte cells healthy by:
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Monocytes are essential to a healthy immune system. They’re like your body’s firefighters. They stop germs from spreading fires (infections) in your tissues and blood. You can keep your monocytes healthy by taking steps to boost your immune system, like getting adequate sleep, eating well-balanced meals and practicing good hygiene to help prevent infection.
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Last reviewed on 01/03/2025.
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