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Eosinophil count (qualitative or semi-quantitative in serum/plasma)

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

This test checks for the presence of eosinophils, a type of white blood cell, in your blood. Eosinophils help fight certain infections and respond to allergic reactions.

Quick summary

["Eosinophil levels may indicate allergies, infections, or other immune responses."]

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

Key facts at a glance

LOINC
16834-4
Short code
E coli K1 Ag Spec Ql LA
Synonyms
E coli K1 Ag Spec Ql LA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
la
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 Might This Test Be Ordered?

Your healthcare provider may recommend this test if you have symptoms like persistent itching, skin rashes, asthma, or unexplained allergies. It could also be used to monitor conditions like parasitic infections, certain cancers, or autoimmune disorders.

What Does the Result Mean?

A qualitative result tells whether eosinophils are present in your blood. Elevated levels may suggest an allergic reaction, parasitic infection, or other inflammatory conditions. Low or absent levels might indicate a normal immune response or certain infections.

What Preparations Are Needed?

No special preparation is usually required. You may eat and drink normally before the test. Avoid taking antihistamines or certain medications that could affect eosinophil counts without consulting your doctor.

What Are Common Causes of Abnormal Results?

Elevated eosinophil counts can be linked to allergies, asthma, parasitic infections, certain cancers (like lymphoma or leukemia), autoimmune diseases, or reactions to medications. Low eosinophil counts are less common but may occur with certain infections or immune deficiencies.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Eos (Serum Eosinophil Screening)

Frequently asked questions

Is there anything I should do if my test results are abnormal?
If your eosinophil count is elevated, your doctor may recommend further testing to identify the underlying cause, such as allergy testing, blood parasite exams, or imaging studies. If low, they may investigate potential infections or immune disorders. Always follow your healthcare provider’s guidance for next steps.
How often will I need this test?
The frequency depends on your condition. Some people may need this test periodically to monitor their symptoms or treatment response. Others may only need it once to diagnose a specific issue. Your doctor will determine the best schedule for you.
Can I fast before this test?
No fasting is required for this test. Since it involves drawing blood, eating and drinking normally is fine. However, always confirm with your healthcare provider before taking any medications, especially those that affect blood counts.
  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