Eosinophils · low result
Low eosinophils: what they mean (and why it is usually nothing)
Short answer
A low eosinophil count (eosinopenia) is an absolute count below about 0.05 × 10³/µL — and since the normal range starts near zero, an eosinophil count of 0% or 0 on a single result is common and, in a healthy person, means nothing. Cortisol suppresses eosinophils, so counts fall during acute infection and physical stress and within hours of a corticosteroid dose; a low count during a febrile illness is in fact a useful clue that the infection is bacterial. Persistently absent eosinophils are rare and point to long-term steroid use, Cushing's syndrome, or marrow suppression. There is no treatment for a low eosinophil count itself.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- A low eosinophil count needs no urgent action on its own. Seek care for the illness it accompanies — fever with confusion, breathing difficulty or low blood pressure is the emergency, not the count.
What is the normal range for Eosinophils?
- age 18+: 1.00 – 4.00 %
Full reference table, citations and testing options: Eosinophils biomarker page.
What are the common causes of low Eosinophils?
- Corticosteroids — prednisone, dexamethasone, injected or high-dose inhaled steroids; eosinophils fall to near zero within hours of a dose
- Acute infection, especially bacterial, and sepsis — the stress response suppresses eosinophils; this is a recognized marker of bacterial rather than viral illness
- Physical stress — surgery, trauma, burns, a heart attack, intense exercise, labor
- Cushing's syndrome and adrenal tumors — chronically high cortisol
- Chemotherapy, radiation, aplastic anemia and other marrow suppression
- Alcohol intoxication, and acute emotional stress or panic
- Normal variation and timing — eosinophils follow a daily rhythm, lowest in the morning when cortisol peaks
- Lab or counting artifact — a 100-cell differential cannot reliably measure a cell type that is normally 1–4% of cells
What symptoms go with low Eosinophils?
- None from the count itself
- Symptoms belong to the cause — fever and the features of an infection; weight gain, round face, easy bruising and high blood pressure with Cushing's
What do clinicians usually check next?
- Check the absolute count and the rest of the CBC; an isolated zero 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 every form, including inhalers, nasal sprays and joint injections
- If a persistent low count comes with weight gain, high blood pressure, easy bruising or new diabetes: screening for Cushing's (late-night salivary cortisol or a dexamethasone suppression test)
- A peripheral smear and hematology referral when other counts are also low
- Nothing further when the result sits inside a normal daily rhythm — morning draws read lower
Follow-up tests available at TestWell: Cortisol Test (AM) ($26.49).
How do you recheck Eosinophils?
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
Is a low eosinophil count bad?
No. The normal range begins near zero, and most healthy people have a result of 0 on at least some CBCs. A low count causes no symptoms and needs no treatment; it is a signal of stress hormones or steroids, not a deficiency.
What does 0% eosinophils mean?
Usually just normal variation, a morning draw, a recent steroid dose or a current infection. A differential that counts a few hundred cells will often record zero for a cell type that is normally 1–4% of them. It is only worth noting if other counts are abnormal.
What causes low eosinophils?
Cortisol — from corticosteroid medication, from the stress of an acute infection or injury, or from Cushing's syndrome. Marrow suppression from chemotherapy is the uncommon cause and lowers the other counts too.
Do steroids lower eosinophils?
Dramatically and within hours; it is one of their most reliable effects. Inhaled and nasal steroids can do it to a smaller degree. The count returns to baseline within a day or two of stopping.
Why would eosinophils be low during an infection?
The stress response raises cortisol, which pulls eosinophils out of the blood. A low eosinophil count during a fever actually favors a bacterial over a viral cause and has been used as a bedside clue for sepsis. The count rebounds as the infection resolves.
Can low eosinophils be a sign of cancer?
Not by itself. Eosinophils fall with marrow suppression from chemotherapy or aplastic anemia, but then neutrophils, hemoglobin and platelets are also low and are the findings that matter. An isolated low eosinophil count is not a cancer signal.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.