Eosinophils (Percent)
The share of your white blood cells that are eosinophils, a cell type involved in allergies and in fighting some parasites.
AI-verified against cited sources. Awaiting expert reviewAlso called EO%, Eos%LOINC 713-8
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What it is
Eosinophils are white blood cells that help the body deal with some parasites and take part in allergic reactions. This result shows what percent of all your white blood cells are eosinophils, and it comes from the white blood cell differential in a CBC. The percent depends on the other white cell types too, so it can change even when the number of eosinophils stays the same. For that reason, clinicians usually rely on the absolute eosinophil count.
Why it matters
The percent gives a quick view of the mix of white blood cells. If it looks high or low, your clinician will usually check the absolute count, which is how eosinophilia is defined. Some labs, including Labcorp, do not set a range for the percent at all.
If it’s low
A low or zero percent is common and usually not a concern. A rise in other white cells, such as neutrophils during an infection or after steroid medicines, pushes the eosinophil share down without much change in the number of eosinophils. Steroid medicines and high cortisol levels can also lower the real count.
Common causes
- Normal variation, since zero is a common result
- A rise in other white cells, such as neutrophils during an infection or stress
- Steroid medicines (corticosteroids)
- High natural cortisol levels, such as with Cushing syndrome
What can help
- Check the absolute eosinophil count and the total white blood cell count
- Tell your clinician about any steroid medicines you take by mouth or injection
If it’s high
A high percent often reflects allergies, asthma, eczema or a reaction to a medicine. It can also rise simply because other white cells are low, which makes the eosinophil share look larger. Check the absolute count. If it is within your lab's range, the high percent may just reflect fewer of the other cells. If the absolute count is high too, see the Eosinophils (Absolute) page. Your clinician can sort out which explanation fits.
Common causes
- Allergies, asthma or eczema
- A reaction to a medicine
- Fewer neutrophils or lymphocytes than usual, which makes the eosinophil share look larger
- Parasite infections, mostly after living in or traveling to certain parts of the world
- Low cortisol from adrenal gland problems
- Immune or blood disorders (less often)
What can help
- Look at the absolute eosinophil count and your total white blood cell count alongside the percent
- Share your allergy history, medicines and travel history with your clinician
- Ask whether a repeat CBC makes 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: 0.4–6.7 %. Source: ARUP Laboratories, Harrison's Principles of Internal Medicine, 19th edition (McGraw-Hill), MedlinePlus Medical Encyclopedia (National Library of Medicine), Labcorp, Orphanet Journal of Rare Diseases, Clinical and Experimental Allergy.
See Eosinophils (%) 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 Eosinophils (%) by age and sex: every percentile as a table, with a download.
What can affect your result
- Changes in other white cell types, which shift the share
- Steroid medicines, which lower the count within days
- Allergy season and asthma flare-ups
- Some medicines, including certain antibiotics, anti-seizure medicines and anti-inflammatory pain relievers
- Whether your lab sets a range: Labcorp prints none, while ARUP lists 0.4 to 6.7 percent
- The percent is a share of all white cells, so it falls when other white cells rise (for example neutrophils during an infection or after steroid medicines) and rises when they fall, even if the number of eosinophils has not changed.
- Steroid medicines (corticosteroids) lower the true eosinophil count within days.
- Some medicines can raise the count, including certain antibiotics, anti-seizure medicines, anti-inflammatory pain relievers and allopurinol.
Within days for steroid-related changes. Medicine-related eosinophilia can take up to about 6 months to settle after the cause is stopped.
When to talk to a clinician
The percent alone rarely needs urgent action. Look at the absolute count: if it is above 1.5 ×10³/µL (1,500 cells/µL), contact your clinician soon, especially if it was high on an earlier test or you have new shortness of breath, chest pain, a spreading rash or swelling. Call 911 or your local emergency number for chest pain, trouble breathing, confusion or fainting.
Questions you could ask
- Should I track the percent or the absolute count over time?
- What is my lab's range for eosinophils, and was anything flagged?
- Is my absolute eosinophil count also high?
- Could allergies or a medicine I take explain this?
- Is my absolute eosinophil count within my lab's range?
Questions people ask
What is a typical eosinophil percentage?
A few percent of your white blood cells. ARUP lists 0.4 to 6.7 percent, and other sources give similar ranges, such as about 1 to 4 or 0.3 to 5 percent. Some labs set no range for the percent.
Why does my report show no range for eosinophil percent?
Some labs, including Labcorp, do not set a range for white cell percents and print 'Not Estab.' (not established). The absolute eosinophil count on the same report is the more useful number.
My eosinophil percent is high but the absolute count is normal. Is that a problem?
It can simply mean that other white cells are low, which makes the eosinophil share look bigger. Your clinician looks at the absolute count to decide whether anything needs follow-up.
How do I get the absolute count from the percent?
Multiply the percent by your total white blood cell count and divide by 100. For example, 3 percent of a white count of 6.0 ×10³/µL is 0.18 ×10³/µL.
Show the science and sources
Units
- 1 % = 1 %
- 1 % = 0.01 fraction (0–1)
Open the Eosinophils (%) unit converter
For clinicians and researchers
Reported as eosinophils per 100 leukocytes (LOINC 713-8 for automated counts and 714-6 for manual counts; LOINC also defines a number-fraction code, 71679-5). Analyzers classify eosinophils by flow cytometry, and a manual differential counts cells on a stained smear. Absolute count equals percent times the total white cell count divided by 100, so 3 percent of a count of 6.0 ×10³/µL is 0.18 ×10³/µL. Because the percent is relative, a shift in neutrophils or lymphocytes changes it independently of the eosinophil number. The published definitions of eosinophilia (0.5 to 1.5 ×10⁹/L) and hypereosinophilia (above 1.5 ×10⁹/L on two occasions at least a month apart and/or tissue eosinophilia) use absolute counts. Reference intervals for the percent are not harmonized: ARUP 0.4 to 6.7 percent, Labcorp not established, and textbook values of about 0.3 to 5 percent.
LOINC 713-8 (primary), 714-6, 26450-7, 71679-5. Specimen: whole-blood.
Sources
- CBC with Platelet Count and Automated Differential (test 0040003), hotline effective March 1, 2021: reference intervals, ARUP Laboratories (2021)
- Normal Values for Leukocyte Concentration in Blood (Table 63-1), Harrison's Principles of Internal Medicine, 19th edition (McGraw-Hill) (2015)
- Blood differential test, MedlinePlus Medical Encyclopedia (National Library of Medicine) (2025)
- Sample patient report, test 005013 (CBC with Diff, Platelet, NLR), Labcorp
- French guidelines for the etiological workup of eosinophilia and the management of hypereosinophilic syndromes, Orphanet Journal of Rare Diseases (2023)
- Blood basophil numbers in chronic ordinary urticaria and healthy controls: diurnal variation, influence of loratadine and prednisolone and relationship to disease activity, Clinical and Experimental Allergy (2003)
- Eosinophil count - absolute, MedlinePlus Medical Encyclopedia (National Library of Medicine) (2025)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.