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Eosinophil count (serum/plasma mass concentration)

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

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

Quick summary

["Eosinophil levels can help diagnose or monitor conditions like allergies, infections, or certain autoimmune diseases."]

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

Key facts at a glance

LOINC
20815-7
Short code
E coli K88 TSMI Ql Aggl
Synonyms
E coli K88 TSMI Ql Aggl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
aggl
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 Is Done

Your healthcare provider may order this test to check for elevated eosinophil levels, which can indicate conditions such as allergic reactions, parasitic infections, asthma, or certain types of cancer. It may also be used to monitor treatment progress for these conditions.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw, where a small amount of blood is taken from a vein in your arm. This is usually quick and painless.

What the Results Mean

Results are typically reported as a count of eosinophils per microliter (µL) of blood. High levels may suggest allergic reactions, infections, or other inflammatory conditions. Low levels might indicate certain immune system issues or stress.

Common Conditions Monitored

Elevated eosinophil levels are often associated with allergies, asthma, parasitic infections, certain cancers (like lymphoma or leukemia), and autoimmune diseases. Low levels may be seen in severe stress, infections, or certain immune deficiencies.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Eosinophil Level

Frequently asked questions

What causes elevated eosinophil levels?
Elevated eosinophil levels can be caused by allergies, asthma, parasitic infections, certain cancers, or inflammatory conditions. Chronic conditions like eosinophilic esophagitis or certain autoimmune diseases may also lead to persistent elevation.
Can low eosinophil levels indicate anything serious?
Low eosinophil levels are less common and may be associated with severe infections, stress (such as trauma or surgery), or certain immune system disorders. They are not typically a standalone indicator of serious illness but may warrant further investigation if unexplained.
How often should I get this test?
The frequency of this test depends on your symptoms, medical history, and ongoing treatment. Your healthcare provider will determine the best schedule based on your specific needs.
  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