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Eosinophil Count (Peripheral 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 and certain inflammatory conditions.

Quick summary

["Eosinophil counts help diagnose and 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
30380-0
Short code
Eosinophil NFr Prt
Synonyms
Eosinophil NFr Prt
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
86592
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

Why This Test Matters

Eosinophils are part of your immune system and can rise in response to allergies, infections, or inflammatory diseases. High levels may signal conditions like asthma, certain infections, or autoimmune disorders. Low levels might indicate immune suppression or other health concerns.

Common Conditions Monitored

Eosinophil counts are often checked in patients with suspected allergies, asthma, parasitic infections, or inflammatory diseases. Doctors may also use this test to evaluate treatment responses or monitor chronic conditions like eosinophilic esophagitis.

How the Test Works

A small blood sample is drawn and examined under a microscope. Special stains highlight eosinophils, allowing the lab to count them accurately. This method is quick and provides a snapshot of your immune cell activity.

Preparation for the Test

No special preparation is needed. You may eat and drink normally before the test, but avoid smoking or excessive caffeine for 30 minutes before drawing blood to avoid temporary changes in white blood cell counts.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Eosinophil CBC

Frequently asked questions

What does an elevated eosinophil count mean?
An elevated eosinophil count (above typical reference ranges) may indicate conditions like allergies, asthma, parasitic infections, or certain inflammatory diseases. Your doctor will consider your symptoms, medical history, and other test results to determine the cause.
What does a low eosinophil count mean?
A low eosinophil count may suggest immune suppression, certain infections, or medications that affect white blood cell production. It could also be normal if your body naturally has fewer eosinophils.
How often should I get this test?
Your doctor will decide how often to check this test based on your health needs. It may be part of routine blood work, monitoring a specific condition, or evaluating symptoms like persistent itching, wheezing, or unexplained rashes.
  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