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Eosinophil count (per microliter of whole blood)

Published: August 9, 2026Updated: August 17, 2026

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

Quick summary

["Eosinophils help protect your body from harmful substances and infections."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
102735-8
Short code
Eggplant IgG RAST
Synonyms
Eggplant IgG RAST
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
rast
CPT
84484
SNOMED
302774002
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 Are Eosinophils?

Eosinophils are a type of white blood cell that play a role in defending your body against parasites, allergies, and certain infections. They release chemicals to attack these threats. When levels are too high or too low, it may signal underlying health concerns.

Why Might You Need This Test?

Your doctor may order this test to diagnose or monitor conditions like allergies, asthma, parasitic infections, or certain autoimmune diseases. High eosinophil counts can also be linked to conditions such as eosinophilic esophagitis or certain cancers.

How Is the Test Performed?

A small blood sample is taken from your arm using a needle. The sample is then sent to a lab where it is analyzed under a microscope to count the eosinophils.

What Are the Possible Results?

Results are typically reported as the number of eosinophils per microliter of blood. While specific reference ranges can vary, elevated or low counts may prompt further testing or evaluation of your symptoms.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Eosinophil blood count

Frequently asked questions

What causes an elevated eosinophil count?
Elevated eosinophil counts can result from allergies, asthma, parasitic infections, certain autoimmune diseases, or conditions like eosinophilic esophagitis. Chronic conditions, stress, or medications may also play a role.
What does a low eosinophil count mean?
A low eosinophil count may suggest immune system issues, certain infections, or conditions affecting white blood cell production. It can also occur with certain medications or in people with severe illness.
Can lifestyle changes affect eosinophil levels?
Yes, lifestyle factors like diet, stress, and exposure to allergens can influence eosinophil counts. Managing allergies, avoiding known triggers, and maintaining overall health may help stabilize these levels.
  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 17, 2026. · Read our editorial policy