Monocytes are a type of white blood cells that are responsible for isolating and cleaning up germs and other harmful microbes from the tissues in the body. They also clean up dead cells and assist in the immune response. Typically, monocytes make up a very small percentage of the total white blood cells in the body. They are present in a concentration of 2-8% (or 100 to 700 per mm3).

What is monocytosis?
When the body’s monocyte count goes above normal levels, it is called monocytosis. This condition is often closely associated with infectious and autoimmune diseases, blood disorders, and certain types of cancer.

Some conditions that can cause monocytosis include endocarditis, tuberculosis, malaria, syphilis, collagen vascular disorders, sarcoidosis, protozoal or rickettsial infections, bone marrow recovery, chronic stress, heart attack, splenectomy, myeloproliferative diseases, or viral infections.

Symptoms of monocytosis
People with a high monocyte count may not experience any symptoms. Generally, symptoms are related to the underlying cause and may include:

• Fatigue
• Weakness
• Swelling
• Fever

To confirm a high monocyte count, doctors prescribe a blood differential test. This test determines the level of each type of white blood cell in the body and informs of any abnormalities in these cells. Normal ranges of the other types of white blood cells in the body are as follows:

• Basophils secrete chemicals such as histamine to help the body’s immune response. They make up 0.5 to 1 percent (25 to 100 per mm3) of one’s white blood cells.
• Eosinophils aid the body’s allergic response and are particularly important for killing cancer and parasitic cells. They make up 1 to 4 percent (50 to 500 per mm3) of white blood cells in the body.
• Lymphocytes comprise about 20 to 40 (1000 to 4000 per mm3) percent of white blood cells and are responsible for creating antibodies that fight against bacteria and viruses.
• Neutrophils are the most common type of white blood cells, making up 55 to 70 percent (2500 to 8000 per mm3) of their content in the body. They form the first line of defense against bacteria and fungi.
• Young neutrophils (band cells)  are immature, commonly produced white blood cells. They make up between 0 and 3 percent of the white blood cell content in the body and are responsible for fighting infections and promoting healing.

A monocyte count of over 10% (or 800 mm3) is considered high and may be an indication of an immune system response to another condition.

Diagnosis and treatment
Based on one’s symptoms and physical examination, doctors may suggest getting additional diagnostic tests such as a chest X-ray, blood smear, urine culture, blood culture, throat culture, and/or a bone marrow biopsy. Depending on the results from these tests, the doctor will draw a diagnosis, such as an infection or health condition that requires attention. The most common tests prescribed are:

• Complete blood count (CBC)
  In this test, a sample of one’s blood is taken to analyze the total number of white blood cells present.
• Peripheral blood smear
  In this test, a blood sample is analyzed under a microscope to assess the cell size and shape. It helps narrow down the list of potential underlying causes that may result in a high monocyte count.
• Absolute monocyte count
  This test measures the number of monocytes in the blood sample. It is based on multiplying the number of monocytes in the CBC by the total number of white blood cells in the sample to examine whether the monocyte count is low, normal, or high.

The treatment for monocytosis will depend on the underlying causes. Some common treatment options include:

• Symptom management for viral infections
• Using antibiotics to treat bacterial infections
• Chemotherapy, radiation therapy, stem cell transplant, supportive therapy, or surgery for treating blood cancer
• Test-based prescriptions for other parasitic conditions

For some conditions, especially some forms of leukemia, blood levels may need to be monitored regularly to monitor the effect of the treatment.

Steps to maintain a healthy monocyte count
Besides formal treatment, one may also use the following techniques to keep monocytes in a healthy range:

• Regular exercise
  Some studies suggest that regular exercise can help maintain monocyte counts at optimal levels and bolster overall health with age.
• Eating anti-inflammatory foods
  Monocytes respond to inflammation in the body. To lower their levels, eating anti-inflammatory foods can help. Some options include olive oil, green leafy vegetables such as kale, spinach, and collard greens, tomatoes, strawberries, blueberries, cherries, oranges, nuts such as almonds and walnuts, and fatty fish such as salmon, tuna, sardines, and mackerel.
  At the same time, avoiding inflammatory foods such as processed or red meats, refined carbohydrates, fried foods, soda, and other sugar-filled beverages, margarine, shortening, and lard is advisable.
• Reduce stress levels
  It is also important to regulate stress levels and get adequate rest to regulate the monocyte count in the body.

A high monocyte count may indicate a serious health condition, infection, or stress. It is advisable to consult a doctor to diagnose the underlying cause and discuss treatment options.