Monocytes are a type of white blood cell that helps fight infections in your body. A high monocyte level may indicate inflammation, infection, blood disorders, and other health issues.

Along with other types of white blood cells, monocytes are a key element of your immune response. High levels can result from a range of issues, including:

But it’s worth noting that doctors interpret monocyte levels in the context of other factors and tests. A high monocyte level is not enough to diagnose any health issue.

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

Your blood contains red and white blood cells, platelets, and plasma. Only about 1% of your blood is comprised of white blood cells, but they play a considerable role in protecting you from illness. Your bone marrow produces five types of white blood cells, each with a specific purpose. These include:

  • Monocytes isolate and clean up germs and other harmful microorganisms. They also get rid of dead cells and assist in the immune response.
  • 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 responses.
  • Lymphocytes produce antibodies against bacteria, viruses, and other invaders.
  • Neutrophils treat bacterial and fungal infections.

The lifespan of white blood cells can vary from hours to years, depending on the type, and 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. Labs typically list each type of white blood cell 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 relatively small percentage of your white blood cells. They can be called absolute monocytes or “monocytes (absolute)” in blood test results that report the count.

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

  • Monocytes: 2 — 8% (100 to 700 per mm3, or cells per cubic millimeter)
  • Basophils: less than 1%
  • Eosinophils: 1 — 4%
  • Lymphocytes: 20 — 40%
  • Neutrophils: 55 — 70%

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

Should I be worried if my monocytes are high?

A high monocyte count usually means your body is fighting some kind of viral, bacterial, or parasitic infection. Less commonly, it might indicate an autoimmune disease, blood disorder, or cancer. A doctor can determine what is causing your high count and recommend treatment.

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

In many cases, the balance between different types of white blood cells helps doctors determine the cause.

The following conditions 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.

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

You’ll need a blood differential test to know how many monocytes are circulating in your blood. 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 like most other blood tests. A medical professional will draw a blood sample 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.

A doctor may order a blood differential test and a complete blood count to help diagnose infection or other conditions, like anemia.

Treatment of elevated monocytes depends on the cause. A 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 like leukemia can include:

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

Regular exercise can promote overall good health and help you maintain typical blood counts. Some evidence suggests exercise can help improve monocyte function, especially as you age.

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

  • fresh vegetables
  • fruit
  • nuts
  • seeds
  • fish
  • olive oil
  • whole grains

If your monocyte level is too high, a doctor can determine the cause, whether you need treatment, and if lifestyle changes may be helpful.

What infections cause high absolute monocytes?

Viral infections, such as infectious mononucleosis, mumps, and measles, are the most common cause of a high absolute monocyte count.

Other infections that can cause high absolute monocytes include:

What cancers cause high monocytes?

Chronic myelomonocytic leukaemia (CMML) is a rare type of blood cancer that can cause elevated levels of monoctyes in the blood. Lymphoma and multiple myeloma may also cause high monocyte levels.

What level of monocytes indicates leukemia?

People with chronic myelomonocytic leukemia (CMML) typically have monocyte counts of at least (at least 1,000 per mm3). They may also have lower numbers of other white blood cells, red blood cells, and platelets.

Doctors must order additional tests, including looking at blood cells under a microscope, to diagnose leukemia.

What is an alarming level of monocytes?

Doctors consider your level of monocytes high if it is above 10% or 800 per mm3. This level may indicate an underlying cause that requires treatment.

The World Health Organization defines persistent monocytosis as an absolute monocyte count > 1 × 109/L with monocytes accounting for > 10% of leukocytes persisting for > 3 months.

What should I do if my monocytes are high?

Depending on the percentages of your other white blood cell counts, a doctor may be able to diagnose the cause. Sometimes, a doctor may need to order additional tests to discover why your levels are high. They will typically recommend treatment for the underlying cause.

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.