Monocytes (Absolute)
The number of monocytes in a microliter of blood. Monocytes are white blood cells that clear debris and help fight infection.
AI-verified against cited sources. Awaiting expert reviewAlso called AMC, Mono#, MONO#LOINC 742-7
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What it is
Monocytes are white blood cells made in your bone marrow. They travel in the blood for a short time, then move into your tissues, where they become macrophages. Macrophages engulf germs and dead cells and help direct the immune response. This test counts how many monocytes are in a set amount of blood. It is part of the differential on a CBC.
Why it matters
Monocyte counts often rise during and after infections and with long-lasting inflammation. They also tend to rise as the body recovers from a drop in blood counts. A high count is a clue that your body is responding to something. A count that stays high for months with no clear reason is something clinicians like to look into. A low count is uncommon on its own and is usually seen together with other low blood counts.
If it’s low
A low monocyte count (monocytopenia) is uncommon on its own. It is often seen together with low counts of other blood cells, or during illness or certain treatments. The same textbook defines it as below 0.2 ×10³/µL, and some labs' ranges start as low as 0.1, so a small dip is often not meaningful.
Common causes
- Corticosteroid (steroid) medicines
- Acute illness, including viral infections such as Epstein-Barr virus, and sepsis
- Treatments that lower all blood counts, such as chemotherapy
- Hemodialysis
- Bone marrow conditions that lower several blood counts, such as aplastic anemia
- Rarely, hairy cell leukemia, which can cause a very low count
What can help
- Ask your clinician to look at your other blood counts alongside this one
- Ask whether to repeat the count after an illness or after treatment ends
If it’s high
A high monocyte count (monocytosis) is usually a reaction to something else, often an infection, inflammation or recovery from an illness. One hematology textbook defines it as above 1.0 ×10³/µL in adults. Labs start flagging results somewhere between about 0.8 and 1.0 ×10³/µL.
Common causes
- Recovery from an infection or from a temporary drop in blood counts
- Longer-lasting infections such as tuberculosis, endocarditis or some fungal and parasite infections
- Inflammatory and autoimmune conditions such as inflammatory bowel disease, lupus, rheumatoid arthritis or sarcoidosis
- Having had the spleen removed
- Some medicines, including growth-factor injections (G-CSF) and olanzapine
- Less often, blood or lymph conditions such as Hodgkin lymphoma or myelodysplastic and related bone marrow disorders
What can help
- Ask your clinician whether a recent illness or a medicine could explain it, and whether to repeat the test after you recover
- If it stays high with no clear reason, ask whether a blood smear review or other tests make sense
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 0.1–0.9 ×10³/µL. Source: Labcorp, Mayo Clinic Laboratories, ARUP Laboratories, Te Whatu Ora Health New Zealand, Waikato, Elsevier.
- Adults (this one applies)0.1–0.9 ×10³/µL
Sources: Labcorp, Mayo Clinic Laboratories, ARUP Laboratories, Te Whatu Ora Health New Zealand, Waikato, Elsevier
See Monocytes (abs) by age and sex, with the U.S. survey numbers where they exist.
How common is your level?
NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.
Use the left and right arrow keys to read each age. Shift moves five years.
Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.
Explore Monocytes (abs) by age and sex: every percentile as a table, with a download.
What can affect your result
- Recent or ongoing infection and recovery from illness
- Inflammation or autoimmune conditions
- Medicines: steroids can lower it, and growth-factor injections can raise it
- Age: children's usual ranges differ from adults'
- Lab differences: adult lower limits run from 0.1 to 0.3 ×10³/µL and upper limits from 0.8 to 1.0 across the labs reviewed
- Manual versus automated counting, since large lymphocytes and young cells can be counted differently
- Recent or ongoing infection, and recovery from illness or from a temporary drop in blood counts, can raise monocytes.
- Corticosteroid medicines can lower monocytes. Growth-factor injections (G-CSF) and some other medicines can raise them.
- Large lymphocytes and young cells can be hard for analyzers to tell from monocytes, so the lab may review a blood smear under the microscope.
- A difficult draw, a clotted sample or a sample that is too old can throw off cell counts.
Can change within days as an infection or inflammation comes and goes.
When to talk to a clinician
A monocyte count rarely needs urgent attention by itself. Talk with a clinician if your count stays above about 1.0 ×10³/µL for several months without a clear reason, or if a high or low count comes with fever, night sweats, unexplained weight loss, frequent infections or other low blood counts. If you feel very unwell, call 911 or your local emergency number.
Questions you could ask
- How does my result compare with my earlier counts?
- Is the range on my lab report the right one for me?
- Could a recent infection, inflammation or a medicine explain this result?
- Should we repeat the count after I have recovered?
- Are my other blood counts also lower than usual?
- Could a medicine or a recent illness explain it?
Questions people ask
Is a high monocyte count usually serious?
Most often it is a reaction to an infection, inflammation or recovery from an illness, and it settles over time. A clinician looks at it together with your other blood counts, your symptoms and how long it lasts.
Why do the monocyte percent and the absolute count sometimes seem to disagree?
The percent is a share of all your white cells, and the absolute count is the actual number. If another white cell type is unusually high or low, the percent can move even when the number of monocytes has not changed. The absolute count is usually the more useful one.
How do I convert between ×10³/µL, ×10⁹/L and cells/µL?
×10³/µL, K/µL, thou/mm³ and ×10⁹/L are the same number, so 0.6 in one is 0.6 in the other. Cells/µL is 1,000 times larger, so 600 cells/µL equals 0.6 ×10³/µL.
Why does my lab's range differ from another lab's?
Each lab sets its range using its own equipment and reference group. Among the labs reviewed here, adult lower limits run from about 0.1 to 0.3 and upper limits from about 0.8 to 1.0 ×10³/µL. Use the range printed on your own report.
Show the science and sources
Units
- 1 ×10³/µL = 1 ×10³/µL
- 1 ×10³/µL = 1 ×10⁹/L
- 1 ×10³/µL = 1000 cells/µL
Open the Monocytes (abs) unit converter
Is a change real?
Monocytes (abs) naturally varies about 12.85% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 40% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Systematic review and meta-analysis of within-subject and between-subject biological variation estimates of 20 haematological parameters (Coskun A et al., EFLM WG-BV).
For clinicians and researchers
The absolute monocyte count is the WBC multiplied by the monocyte fraction. Analyzers identify monocytes by size, granularity and staining or fluorescence. Large lymphocytes, immature cells and other atypical cells can overlap with the monocyte region, so some results trigger a smear review. Textbook definitions are monocytosis above 1.0 ×10⁹/L in adults (above 3.5 in neonates) and monocytopenia below 0.2 ×10⁹/L. Monocytopenia is rare unless other cell lines are also low. Monocytosis is associated with many conditions because of the cell's role in infection, inflammation, immune reactions and tissue repair, and a transient rise is often the first sign of recovery after myelosuppression. Persistent monocytosis without a reactive cause, especially with atypical morphology or other cytopenias, is followed up with smear review and sometimes further testing, because clonal conditions such as myelodysplastic and myeloproliferative neoplasms and monocytic leukemia are among the possible causes. Adult reference intervals vary by lab: Labcorp 0.1–0.9, Mayo 0.26–0.81, ARUP 0.3–1.0 and Waikato 0.2–1.0 ×10⁹/L.
LOINC 742-7 (primary), 26484-6, 743-5. Specimen: whole-blood.
Sources
- CBC With Differential/Platelet, sample patient report (test 005009), Labcorp
- Complete Blood Cell Count (CBC) with Differential, Blood (test ID CBC), Mayo Clinic Laboratories
- CBC with Platelet Count and Automated Differential (test 0040003), hotline effective March 1, 2021, ARUP Laboratories (2021)
- CBC reference intervals (HEM-2597.01), Te Whatu Ora Health New Zealand, Waikato (2024)
- Nonmalignant leukocyte disorders (Rodak's Hematology, 6th edition), Elsevier (2019)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.