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Eosinophil count (peripheral blood, qualitative)

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

This test checks the number of eosinophils, a type of white blood cell, in your blood. Eosinophils help fight infections and respond to allergies or inflammation.

Quick summary

["Eosinophils help identify certain infections, allergies, or inflammatory conditions."]

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

Key facts at a glance

LOINC
30377-6
Short code
Eosinophil NFr Bronch
Synonyms
Eosinophil NFr Bronch
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is an Eosinophil?

Eosinophils are a type of white blood cell that plays a role in defending the body against parasites, allergies, and certain infections. They also help regulate inflammation. When levels are unusually high, it may signal an underlying condition like asthma, allergies, or certain infections.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like persistent coughing, wheezing, skin rashes, or unexplained fatigue. It can also help diagnose conditions like parasitic infections, certain cancers, or autoimmune diseases.

Common Reasons for Testing

Elevated eosinophil counts are sometimes seen in conditions like asthma, allergic reactions, parasitic infections, or certain blood disorders. Low levels may indicate immune suppression or other systemic issues.

How Is the Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The sample is then examined under a microscope to count eosinophils. No special preparation is needed, but fasting may not be required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated eosinophils can indicate active allergic reactions, parasitic infections, certain lung diseases (like eosinophilic pneumonia), or conditions like hypereosinophilic syndrome. Low levels may suggest immune dysfunction or other underlying health concerns.

Short name

Eosinophil test

Frequently asked questions

What Does a High or Low Eosinophil Count Mean?
A high eosinophil count may suggest an allergic reaction, asthma, or parasitic infection. A low count could indicate a weakened immune response or other health issues, but results depend on your overall symptoms and medical history.
Does This Test Require Special Preparation?
No special preparation is needed, but avoid heavy meals or strenuous activity before your blood draw if instructed by your doctor.
How Long Does It Take to Get Results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
  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