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Eosinophil count (per microliter of whole blood)

Published: August 9, 2026Updated: August 16, 2026

This test measures the number of eosinophils, a type of white blood cell, in your blood. Eosinophils help fight infections caused by parasites and play a role in allergic reactions.

Quick summary

["Eosinophil levels can help diagnose or monitor conditions affecting your immune system or allergies."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
45379-5
Short code
Eosinophil Stl Ql Micro
Synonyms
Eosinophil Stl Ql Micro
Category
chemistry
Sample
stool
Container
Clean container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
microscopy-light
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

Why This Test Matters

Eosinophils are a type of white blood cell that can rise in response to certain infections, allergies, or inflammatory conditions. High levels may suggest conditions like asthma, allergies, parasitic infections, or certain autoimmune diseases. Low levels might indicate immune suppression or other health concerns.

When You Might Need This Test

Your doctor may order this test if you have symptoms like persistent coughing, wheezing, skin rashes, or unexplained fatigue. It’s also used to monitor conditions like asthma, eosinophilic esophagitis, or chronic infections.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or hand to draw blood. The process takes about 5 minutes, and you may feel a brief pinch.

What the Results Mean

Results are typically reported as the number of eosinophils per microliter of blood. While reference ranges vary by lab, elevated counts (above normal) may signal allergic reactions, infections, or inflammatory diseases. Your doctor will interpret results in the context of your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Eosinophil test

Frequently asked questions

What causes high eosinophil levels?
High eosinophil counts can result from allergies, asthma, parasitic infections, certain cancers (like leukemia), or inflammatory conditions. Chronic conditions like eosinophilic granulomatosis with polyangiitis (EGPA) may also be linked to elevated eosinophils.
What causes low eosinophil levels?
Low eosinophil counts can occur due to immune suppression (e.g., from medications like steroids), severe infections, or blood disorders. Rarely, it may indicate genetic or metabolic conditions.
How often should I get this test?
Your doctor will determine the frequency based on your symptoms, diagnosis, or treatment plan. Follow-up tests may be scheduled if your condition requires monitoring, such as for asthma or allergic reactions.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy