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.

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

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.

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.

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 parasitic infections or bacterial infections, including tuberculosis.

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.

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.

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.

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.