Eosinophil percentage optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for Eosinophil percentage:

  • Optimal 1 – 3 %; sufficient 1 – 4 %; out of range below 1 or above 4 %.

Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.

All units

UnitOptimalSufficientOut of range
%1 – 31 – 4below 1 or above 4

What the evidence says

The acceptable band of 1% to 4% is the reference interval MedlinePlus gives; some laboratories use 0% to 8%. The optimal ceiling of 3% has no published source. A result below 1% has no accepted clinical meaning on its own. The absolute eosinophil count is the more meaningful figure, since a percentage shifts whenever another cell type changes; it rises with allergic activity and certain infections.

Sources

  • Blood differential test — MedlinePlus Medical Encyclopedia, US National Library of Medicine, 2025 · Government / public-health guidanceNormal eosinophils are 1% to 4% of white cells, the same as Sera's sufficient band.
  • AUTO DIFF (test catalog entry) — MHCC Laboratory, test catalog powered by Mayo Clinic Laboratories, 2026 · Laboratory / reference-interval sourceAdult eosinophils 0% to 8%: no lower limit, and an upper limit twice Sera's 4%. The page shows no review date; 2026 is the copyright year.

What Eosinophils % measures

The share of your white blood cells that are eosinophils.

Raised in allergies, asthma, and parasite infections.

Related blood cell health markers

See Eosinophil percentage in the full list of biomarker ranges

About the author

Alina Radu is the founder of Sera and a software engineer. The idea started with her own Hashimoto's tests, scattered across years without the big picture. She is not a clinician: these ranges are compiled from the published sources linked on each page, with every source named. Alina Radu on LinkedIn

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.