Monocytes are the largest of all white blood cells and play an important role in the defense against germs and in inflammation. Read on to learn about these cells, the health effects of having higher or lower levels of monocytes, and how to keep your monocytes in the normal range.
Monocytes also play a role in controlling and mitigating the effects of Th1/Th2/Th17 dominance, which is an important factor in chronic inflammation, leaky gut, and more.
What are Monocytes?
The Forefront of Your Immunity
Monocytes are the largest type of white blood cell. Approximately 2 to 10% of white blood cells are monocytes .
Monocytes protect against viral, bacterial, fungal, and protozoal infections .
In adults, blood cells are produced mainly in the bone marrow.
All blood cells originate from common parent cells called hematopoietic stem cells .
The process of monocyte production is called myelopoiesis .
Factors that control this process are:
- Transcription factor SPI1 [10, 11, 12, 13].
- Cytokines: SCF (stem cell factor), GM-CSF (granulocyte-macrophage-colony-stimulating factor), M-CSF (macrophage colony-stimulating factor, CSF1), IL-3, IL-6, and IFN-gamma [14, 15, 16, 17].
After Monocytes Fulfill Their Job, What Happens Next?
Monocytes live for an average of 3 days before undergoing apoptosis (programmed cell death) .
Normal Monocytes Reference Ranges
The normal ranges for Monocytes are:
- 0.2 – 0.8 x10^9/L
- 200 – 800 / microL
- 1 – 10%
Having an optimal monocyte count means you have a lower risk of:
- Viral, bacterial, and fungal infections 
- Heart Disease 
- Obesity 
- Diabetes 
- Death (mortality) 
Other Suggested Marker Tests if your monocytes are out of the optimal range:
High Levels of Monocytes (Monocytosis)
In monocytosis, the number of monocytes circulating in the blood is increased to more than 0.8×109/L in adults.
Conditions Associated with Monocytosis
- Blood disorders (myelodysplastic disorder, acute monocytic, chronic myelomonocytic leukemia, Hodgkin and non-Hodgkin lymphoma) [24, 25, 26]
- Infections (tuberculosis, viral infections, bacterial endocarditis, brucellosis, malaria, syphilis) [27, 28, 29, 30, 31, 32]
- Autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease) [33, 34, 35]
- Sarcoidosis 
- Cancers (ovary, breast, rectum) [27, 37]
- Heart attack [27, 38]
- Appendicitis 
- HIV infection [27, 40]
- Depression 
- Childbirth [42, 43]
- Obesity 
- Severe pneumonia 
- Alcoholic liver disease 
Symptoms and Causes
Monocytosis most commonly occurs during and after chronic inflammation or infection .
The main causes of high monocyte levels are:
- Chronic (long-term) inflammation 
- Infections, such as tuberculosis, malaria, and syphilis [48, 49, 50]
High monocyte levels may also be caused by:
- Autoimmune diseases, such as lupus, rheumatoid arthritis, and IBD [35, 33, 34]
- Leukemias, such as chronic myelomonocytic leukemia, and juvenile myelomonocytic leukemia [51, 52]
- Cancer 
- Depression 
- Obesity 
There are rarely any symptoms that go along with monocytosis itself. Instead, the symptoms mostly come from the diseases associated with monocytosis . These symptoms include:
1) Increase the Risk of Atherosclerosis
Monocytes and macrophages are involved in the development and worsening of atherosclerosis (hardening of the arteries) that can lead to heart disease and stroke .
As hardening of the arteries progresses, the number of monocytes in the blood rises .
2) May Increase Inflammation in Diabetes
A clinical study showed no effect of diabetes on the number of circulating white blood cells, but monocytes were significantly increased .
Monocytes may induce inflammation in diabetes.
<h4″>3) May Increase the Risk of Death in the Elderly
Monocytosis is associated with an increased risk of cardiovascular and cancer-related death in the elderly .
4) Boost the Healing Process After a Heart Attack
Ways to Decrease Levels
1) Regular Exercise
Regular exercise is anti-inflammatory. Monocytes significantly decreased after a 6-week course of moderate-intensity cycling in overweight sedentary women.
2) Weight Loss
3) Omega-3 Fatty Acids
People taking fish oil supplements were less likely to have inflammation in the blood vessel walls caused by monocytes. This effect was not as pronounced in people already taking medication to treat peripheral artery disease .
<h4″>4) Mediterranean Diet
The Mediterranean diet is comprised of foods such as seeds, nuts, vegetables, fruits, whole grains, and monounsaturated fats from olive oil.
5) Moderate Alcohol Intake
Alcohol influences monocyte function .
Studies suggest that acute alcohol consumption decreases inflammation in response to LPS in the gut .
These mechanisms may contribute to the beneficial effects of moderate alcohol use on atherosclerosis.
Drugs and Hormones That Decrease Monocytes
1) Cortisol and Glucocorticoids
A single dose of cortisol decreased monocytes by 90% at 4 to 6 hours after treatment. This reduction persisted for about 24 hours. Subsequently, monocyte levels returned to normal 24 to 72 hours after treatment .
2) Estrogen and Progesterone
Infliximab kills monocytes, which may help reduce inflammation in patients with chronic inflammatory diseases .
Low Levels of Monocytes (Monocytopenia)
In monocytopenia, the number of monocytes circulating in the blood is decreased to less than 0.2×109/L in adults. Monocytopenia itself does not have symptoms, and patients usually only show symptoms related to its associated diseases, such as fatigue and fever [20, 85].
Conditions Associated with Monocytopenia
- Aplastic anemia 
- Leukemia (hairy-cell leukemia, chronic lymphocytic leukemia) 
- Chemotherapy 
- MonoMAC syndrome (monocytopenia and Mycobacterium Avium Complex syndrome) 
- Severe burn injuries 
- Rheumatoid arthritis 
- Systemic lupus erythematosus 
- HIV infection 
- Vitamin B12 deficiency 
- Corticosteroid therapy (transient monocytopenia) 
- Administration of INF-alpha and TNF-alpha 
- Radiation therapy 
1) Lower the Risk of Cardiovascular Disease
Out of all white blood cells, monocyte count has the strongest relationship with overall cardiovascular disease development in people with no symptoms.
Lower levels of monocytes are associated with lower cardiovascular risk .
2) Increase Susceptibility to Infections
Low monocyte counts increase susceptibility to infections.
3) May Increase the Risk of Blood Disorders
Monocytopenia is associated with a high risk of blood disorders such as myelodysplasia, acute myelogenous leukemia, chronic myelomonocytic leukemia, and lymphomas .
4) May Increase the Risk of Cervical Cancer
Due to monocytopenia, patients with primary immunodeficiency are susceptible to severe, persistent human papillomavirus (HPV) infections that may cause cervical cancer .
Ways to Increase Monocyte Levels
1) Acute Strenuous Exercise
3) Cold Exposure
Prolonged cold exposure increases the number of monocytes through the “fight-or-flight” (sympathetic) nervous system activation .
6) Vitamin B12
Vitamin B12 helps increase white blood cell count (including monocytes) in rats with protein deficiencies. However, supplementation with vitamin B12 does not change white blood cell count in rats that ate normal amounts of protein .
7) Vitamin C
8) Calcitriol (Vitamin D)
Garlic increases the total white blood cell count. Rats fed garlic had significantly more monocytes, neutrophils, and lymphocytes than rats not fed with garlic .
Factors That Increase Monocytes
Leptin levels correlate with body weight.
3) Chronic Alcohol Drinking
Alcohol consumption causes leaky gut, which allows lipopolysaccharides (LPS) from gram-negative bacteria in the gut to cause inflammation. Acute alcohol consumption initially lowers inflammation.
However, chronic alcohol consumption can raise monocytes and inflammatory proteins, contributing to widespread inflammation. Prolonged alcohol intake also increases TNF-alpha production by monocytes [77, 110, 111].
4) Growth Hormone
Irregular Monocyte Levels?
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Monocytes are your largest white blood cells that kill microbes, recycle old cells, and boost immunity. Keeping your monocytes within the normal range (0.2 – 0.8 x10^9/L) will lower your risk of infections and chronic diseases.
The most common causes of high monocytes (monocytosis) are chronic infections and inflammation. In turn, high monocytes can worsen inflammation and clog your blood vessels.
To lower your levels, make sure to exercise regularly, lose extra weight, and follow a Mediterranean-style diet.
Many health conditions can also cause low monocyte levels (monocytopenia), including autoimmune diseases and nutrient deficiencies. Having low monocytes may reduce your risk of heart disease but makes you more prone to infections and blood disorders.
To increase your monocyte count, try cold exposure, saunas, and exercise. Vitamins C, D, B12, and garlic may also help.