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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 certain infections and respond to allergies and inflammation.

Quick summary

["Eosinophils help your body defend against parasites and allergic reactions."]

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

Key facts at a glance

LOINC
90297-3
Short code
E histolyt Ab Ser Ql IA
Synonyms
E histolyt Ab Ser Ql IA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 immune responses, particularly against parasites, allergens, and some infections. They release chemicals that help fight off harmful organisms and reduce inflammation in allergic reactions.

Why Might This Test Be Ordered?

Your doctor may order this test if you have symptoms like persistent itching, skin rashes, asthma, or unexplained allergies. It could also be used to diagnose conditions like parasitic infections, certain types of asthma, or eosinophilic disorders.

When Might You Need This Test?

You might need this test if you have symptoms linked to eosinophil-related conditions, such as chronic coughing, unexplained weight loss, or skin problems. It may also be part of a broader evaluation for immune system disorders.

What to Expect Before the Test

No special preparation is usually needed. A blood sample is drawn from a vein, typically in your arm. This is a quick and safe procedure, and you can resume normal activities afterward.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated eosinophil counts may indicate allergic reactions, parasitic infections, certain lung diseases (like eosinophilic pneumonia), or autoimmune conditions. Low levels might suggest immune deficiencies or other underlying health issues, though this is less common.

Short name

Eosinophil count

Frequently asked questions

When could my eosinophil count be higher than normal?
Your eosinophil count could be higher than normal due to allergies, asthma, parasitic infections, certain cancers (like lymphoma), or inflammatory conditions. Your doctor will review your symptoms and test results to determine the cause.
What does it mean if my eosinophil count is low?
A low eosinophil count is less common and may suggest conditions like immune deficiencies, certain infections, or medications that suppress white blood cell production. Your doctor will consider your overall health and other test results to explain this result.
Can this test help diagnose a specific condition?
Yes, this test can help identify conditions linked to eosinophils, such as allergic disorders or parasitic infections. However, it’s often used alongside other tests and clinical findings to make a full diagnosis.
  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