Monocytes are a type of white blood cell. They help fight bacteria, viruses, and other infections in your body. Along with other types of white blood cells, monocytes are a key element of your immune response.

Let’s take a closer look at monocytes, their role in keeping you healthy, and what it means when your monocyte levels are high.

In addition to platelets and plasma, your blood contains red and white blood cells. Only about 1 percent of your blood is comprised of white blood cells, but they play a huge role in protecting you from illness. There are five types of white blood cells, each with a specific purpose.

Your bone marrow produces monocytes and releases them into your bloodstream. Once they reach tissues in your body, they’re called macrophages.

There, they isolate and clean up germs and other harmful microorganisms. They also get rid of dead cells and assist in the immune response.

Here’s a bit about the other types of white blood cells:

  • Basophils secrete chemicals to help mediate the body’s response to allergies and infectious agents.
  • Eosinophils respond to parasites and cancer cells and assist with allergic response.
  • Lymphocytes produce antibodies against bacteria, viruses, and other invaders.
  • Neutrophils kill bacteria and fungi.

Some types of white blood cells typically only live for 1 to 3 days, so your bone marrow is constantly producing more.

White blood cells live in a delicate balance. When one type is high, another might be low.

Looking at monocytes alone may not give you the whole picture. That’s why each type of white blood cell will be listed as a percentage on your blood test report. This report may refer to the overall count as the leukocyte count. It’s another term for white blood cell count.

Monocytes typically make up a fairly small percentage of your white blood cells. They can be referred to as absolute monocytes or “monocytes (absolute)” in blood test results when a count of monocytes is reported.

The typical percentage range of each type of white blood cell is:

  • Monocytes: 2 to 8 percent (100 to 700 per mm3, or cells per cubic millimeter)
  • Basophils: 0.5 to 1 percent
  • Eosinophils: 1 to 4 percent
  • Lymphocytes: 20 to 40 percent
  • Neutrophils: 55 to 70 percent
  • Young neutrophils (band): 0 to 3 percent

An absolute monocyte count above 10 percent, or 800 per mm3, is considered high. It’s called monocytosis and might mean your body is responding to something.

If your monocyte count is high, you may not have symptoms. Any symptoms you have may be associated with the underlying cause.

In general, symptoms may include:

  • fatigue
  • weakness
  • swelling
  • fever

Your monocyte level and overall white blood count are likely to rise in response to:

  • acute stress
  • blood disorders
  • immune response
  • infection
  • inflammation

In many cases, the balance between different types of white blood cells helps tell the tale.

For example, a 2015 study found that a high-monocyte-to-low-lymphocyte ratio may help identify disease activity in people with ulcerative colitis.

The following are some of the conditions that may be risk factors for elevated monocyte levels:

A high monocyte count is the most common sign of chronic myelomonocytic leukemia, a type of cancer that begins in the cells that produce blood in your bone marrow.

A 2019 study suggests that a higher monocyte count may also be related to cardiovascular disease risk and that early detection of increased monocytes could help assess heart health management. However, more large-scale research is needed to confirm this.

To know how many monocytes are circulating in your blood, you’ll need a blood differential test. This test determines the level of each type of white blood cell in your blood. It can also tell if some types of white blood cells are atypical or immature.

The blood differential test is done the same way as most other blood tests. A medical professional will draw a sample of blood from a vein in your arm. You do not have to fast or do anything in preparation for this test.

Once your blood is drawn, a special dye helps the pathologist count the different types of white blood cells in your blood sample.

It’s a test your doctor might order with a complete blood count to help diagnose infection or conditions, like anemia and leukemia.

Treatment of elevated monocytes depends on the cause. Your doctor may have to do more tests to determine the underlying cause.

Generally, treatment may include the following:

  • Treatment for viral infections usually focuses on symptom management.
  • Antibiotics can treat many bacterial infections, such as TB.
  • There are many types of parasitic diseases. You’ll likely need other lab tests to determine the exact cause before the correct medication can be prescribed.

Treatment for blood cancers can include:

When it comes to white blood cells, you want to keep them all within the healthy range. If your white blood cell count is too low, you’ll be more vulnerable to illness. If it’s too high, it may mean your body is responding to something.

Regular exercise is an important component to overall good health and maintaining the right blood counts. There’s some evidence to suggest exercise can help improve monocyte function, especially as you age.

Since monocytes respond to inflammation, an anti-inflammatory diet might be beneficial. Anti-inflammatory foods include:

  • olive oil
  • green leafy vegetables
  • tomatoes
  • strawberries, blueberries, cherries, and oranges
  • nuts
  • fatty fish, such as salmon, tuna, sardines, and mackerel

Some foods, like those listed below, can increase inflammation. Try to limit:

  • red and processed meat
  • refined carbohydrates, like baked goods, white bread, and white pasta
  • fried foods
  • soda and other sugary drinks
  • margarine, shortening, and lard

The Mediterranean diet is a good example of an anti-inflammatory diet. It includes a lot of fresh vegetables, fruit, nuts, seeds, fish, olive oil, and whole grains.

The white blood cell count is complicated. If you think your monocyte level is too high, talk with your doctor about why that is, whether you need treatment, and if lifestyle changes may be helpful.

Monocytes, along with other types of white blood cells, are a vital part of your immune system. They help protect you against infection and illness.

If your monocytes are higher than they should be, a doctor can work with you to find the cause and start any treatments that may be necessary.

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