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 comprises 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 gobble 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 fight allergies and infectious agents.
  • Eosinophils attack parasites and cancer cells and assist with allergic response.
  • Lymphocytes produce antibodies against bacteria, viruses, and other invaders.
  • Neutrophils kill bacteria and fungi.

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

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 abnormal or immature.

The blood differential test is done the same way as most other blood tests. A sample of blood will be drawn from your arm. You don’t 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 to help diagnose infection or conditions like anemia and leukemia.

White blood cells live in a delicate balance. When one 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 it as a leukocyte count. It’s another term for white blood cell count.

Monocytes typically make up a fairly small percentage of your white blood cells. The normal range of each type of white blood cell is:

Your overall white blood count is likely to rise in response to:

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

When your monocyte level is high — known as monocytosis — it means your body is fighting something.

Some conditions that can cause an increase in the monocytes in your blood are:

Having too many monocytes is also the most common sign of chronic myelomonocytic leukemia. This is a type of cancer that begins in the cells that produce blood in bone marrow.

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

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 can help identify disease activity in people with ulcerative colitis.

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 need 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 means your body is fighting 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 to 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, your doctor will work with you to find the cause and start any treatments that may be necessary.