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 a 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?
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 .
Monocyte Production in the Body
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 range 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:
White blood cell count, neutrophils, eosinophils, lymphocytes, and basophils.
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 
Health Effects of Elevated Levels
The condition of having high monocyte levels is known as monocytosis. This most commonly occurs during- and after chronic inflammation or infection .
Monocytosis has been associated with a greater risk of death (mortality) from any cause .
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 essential to the development and exacerbation of atherosclerosis (hardening of the arteries) that can lead to heart attack, stroke, and heart failure .
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.
3) Associated with Increased Risk of Death in the Elderly
An increased number of monocytes is associated with an increased risk of cardiovascular and cancer-related risk of dying in the elderly .
4) Facilitate 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 .
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.
Factors 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 .
This decrease is thought to be a consequence of the redistribution of monocytes.
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,
- Chemotherapy 
- MonoMAC syndrome (monocytopenia and Mycobacterium Avium Complex syndrome) 
- Severe burn injuries 
- Rheumatoid arthritis 
- Systemic lupus erythematosus 
- Vitamin B12 deficiency 
- Corticosteroid therapy (transient monocytopenia) 
- Administration of INF-alpha and TNF-alpha 
Health Effects Low Levels
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) Are Associated with a Risk of Blood Disorders
Monocytopenia is associated with a high risk of development of hematologic disorders such as myelodysplasia, acute myelogenous leukemia, chronic myelomonocytic leukemia, and lymphomas .
4) Increase the Risk of Cervical Cancer
Due to monocytopenia, patients with primary immunodeficiency are susceptible to severe, persistent human papillomavirus (HPV) infections that can 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 .
4) Growth Hormone
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 from gram-negative bacteria in the gut to cause inflammation. Acute alcohol consumption initially mitigates the inflammation from LPS. However, chronic alcohol consumption can lead to a gradual increase of monocytes and inflammatory proteins, contributing to a general body state of inflammation .
Irregular Monocyte Levels?
LabTestAnalyzer helps you make sense of your lab results. It informs you which labs are not in the optimal range and gives you guidance about how to get them to optimal. It also allows you to track your labs over time. No need to do thousands of hours of research on what to make of your lab tests.
LabTestAnalyzer is a sister company of SelfHacked. The proceeds from your purchase of this product are reinvested into our research and development, in order to serve you better. Thank you for your support.