Monocytes · low result
Low monocytes: what they mean and when it matters
Short answer
A low monocyte count (monocytopenia) is an absolute count below about 0.2 × 10³/µL, or a percentage under the lab's range — and because the normal range is small, a count of zero on a single result is common and usually meaningless. Transient low values occur during acute infections and stress and with corticosteroids, which temporarily move monocytes out of the blood. Persistently low monocytes are uncommon and point to bone-marrow suppression: chemotherapy, radiation, aplastic anemia, hairy cell leukemia (where monocytopenia is a classic clue), or rare inherited conditions such as GATA2 deficiency. A low monocyte percentage with a normal total white count is not monocytopenia at all.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- Fever with low monocytes together with low neutrophils — same-day care; infection risk is driven by the neutrophil count
- Persistent monocytopenia with new bruising, bleeding, severe fatigue or an enlarging spleen — prompt evaluation within days
What is the normal range for Monocytes?
- age 18+: 2.00 – 8.00 %
Full reference table, citations and testing options: Monocytes biomarker page.
What are the common causes of low Monocytes?
- Acute infection and sepsis, and physical stress — a temporary shift of monocytes into tissues
- Corticosteroids (prednisone, dexamethasone) — the count can fall to near zero within hours of a dose and recovers when it is stopped
- Chemotherapy, radiation, and other marrow-suppressing drugs; interferon
- Aplastic anemia and myelodysplastic syndromes — usually with other counts low as well
- Hairy cell leukemia — monocytopenia is one of its characteristic findings, alongside an enlarged spleen and low counts
- HIV infection and other causes of marrow suppression; severe vitamin B12 or folate deficiency
- GATA2 deficiency (MonoMAC) and other rare inherited immune disorders — persistent near-absent monocytes from a young age with unusual infections
- Lab or statistical artifact — a differential that counts 100 cells cannot reliably measure a cell type that is normally 2–8% of them
What symptoms go with low Monocytes?
- None from the count itself
- Unusual or recurrent infections (mycobacteria, fungi, warts) when monocytes are persistently absent
- Fatigue, bruising, infections or an enlarged spleen when the cause is a marrow disorder
What do clinicians usually check next?
- Check the absolute count and the rest of the CBC — an isolated low monocyte percentage with normal totals needs nothing
- Repeat the CBC with differential in 4–6 weeks, off any steroid course and after any illness
- Medication review — corticosteroids in any form, chemotherapy, immunosuppressants
- A peripheral blood smear when the count is persistently very low, especially with low neutrophils, anemia or low platelets
- HIV test, B12 and folate when the picture fits
- Hematology referral when monocytes stay below about 0.1 × 10³/µL on repeat, when the spleen is enlarged, or when other counts are also low — a marrow examination may follow
- Immunology evaluation (including GATA2 testing) for persistent monocytopenia with unusual infections, warts or a family history
Follow-up tests available at TestWell: HIV 1/2 Antigen & Antibodies Test (4th Gen) ($38.99), Folate Test (Vitamin B9) ($21.99).
How do you recheck Monocytes?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Biological Age Panel | Panel · 3 tests | $59.99 | Yes | 1–3 business days |
| General Wellness Panel | Panel · 4 tests | $49.99 | Yes | 1–3 business days |
| Blood Clotting Panel | Panel · 4 tests | $149.99 | No | 3–7 business days |
| CBC with Differential Test | Test · 14 biomarkers | $17.99 | No | 1–3 business days |
Common questions
What is a low monocyte count?
An absolute monocyte count below about 0.2 × 10³/µL (200 per microliter). Because the normal range is small — roughly 0.2–0.8 — a single value at or near zero is common and rarely meaningful; it is persistence, and company from other low counts, that matters.
Is a monocyte count of 0 serious?
Usually not. A differential that counts a few hundred cells can easily miss a type that normally makes up 2–8% of them, and steroids or an acute illness can push monocytes to zero for a day. Repeat it when well; a persistent zero with other counts abnormal is the situation that is investigated.
What causes low monocytes?
Temporarily: acute infection, stress and corticosteroids. Persistently: marrow suppression from chemotherapy or radiation, aplastic anemia, hairy cell leukemia, HIV, severe B12 or folate deficiency, and rare inherited conditions such as GATA2 deficiency.
My monocyte percentage is low but everything else is normal — does it matter?
No. Percentages move whenever neutrophils or lymphocytes move, so a low monocyte percentage with a normal total white count is a normal result. The absolute count is what is read.
Do steroids lower monocytes?
Yes, markedly and quickly — a dose of prednisone or dexamethasone can take monocytes to near zero within hours. The count returns to normal within a day or two of the last dose, so a low value on steroids needs no further action.
Can low monocytes mean leukemia?
Rarely, and in a specific way: hairy cell leukemia classically causes monocytopenia together with an enlarged spleen, fatigue and low counts overall. An isolated low monocyte count with a normal smear and normal other counts is not that picture.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.