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Eosinophil count in serum/plasma (absolute)

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

["Eosinophils help your body defend against certain infections and allergies."]

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

Key facts at a glance

LOINC
56148-0
Short code
ENA SM + RNP Ser
Synonyms
ENA SM + RNP Ser
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 Are Eosinophils?

Eosinophils are a type of white blood cell that helps your body respond to infections and allergic reactions. They are part of the immune system and can increase in number when your body is dealing with parasites, allergies, or certain inflammatory conditions.

Why Might You Need This Test?

Your doctor may order this test to diagnose or monitor conditions such as allergies, asthma, parasitic infections, certain cancers (like leukemia), or other immune-related disorders. It can also help assess how your body is responding to treatments for these conditions.

Common Conditions Monitored

Elevated eosinophil counts may suggest conditions like allergic reactions, asthma, parasitic infections, or certain types of inflammatory diseases. Low levels might indicate immune deficiencies or other underlying health issues.

How Is the Test Performed?

A small amount of blood is drawn from a vein, usually in your arm. The blood sample is then sent to a lab where it is analyzed to count the number of eosinophils present.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Eosinophil counts can provide important clues about your health. High levels may indicate allergic responses, parasitic infections, or certain autoimmune conditions. Low levels might suggest immune system issues or other health concerns that need further evaluation by your healthcare provider.

Short name

Eosinophil Level

Frequently asked questions

What Does an Abnormal Result Mean?
An abnormal result could mean you have an infection, allergy, or another condition affecting your immune system. Your doctor will discuss the results with you and may recommend additional tests or treatments based on the findings.
How Often Should I Get This Test?
The frequency of this test depends on your symptoms, medical history, and treatment plan. Your doctor will determine how often you need it based on your specific situation.
Can I Prepare for This Test?
No special preparation is usually needed for this blood test. However, if you are on certain medications or have specific health conditions, let your doctor know before the test.
  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