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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 or certain allergens.

Quick summary

["Eosinophil levels can indicate allergic reactions, infections, or other immune responses."]

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

Key facts at a glance

LOINC
56922-8
Short code
E histolyt IgG Ser Ql IA
Synonyms
E histolyt IgG 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
CPT
82784
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 You Need This Test?

Your doctor may order this test to diagnose or monitor conditions such as allergies, asthma, parasitic infections, or certain autoimmune diseases. It can also help assess how your body is responding to treatments for these conditions.

What Does an Abnormal Result Mean?

Elevated eosinophil levels may suggest allergic reactions, parasitic infections, or conditions like asthma or certain cancers. Lower-than-normal levels might indicate immune suppression or other underlying health issues. Your doctor will discuss these findings with you in detail.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab where it is analyzed to count the number of eosinophils. The results are compared to standard reference ranges to determine if your levels are within normal limits.

What Can Affect Test Results?

Several factors can influence eosinophil counts, including recent infections, allergies, certain medications (like steroids), stress, or underlying health conditions. It’s important to inform your doctor about any medications or recent health events that might affect the results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Eosinophil count

Frequently asked questions

What Are Common Questions About This Test?
This test is typically not used to diagnose conditions directly but helps guide further investigation or treatment planning. For example, high eosinophil levels might prompt additional testing for allergies or parasitic infections.
How often will I need this test?
The frequency depends on your medical condition and treatment plan. Your doctor will let you know how often you need retests, whether it’s monthly, quarterly, or as needed.
Can I prepare for this test?
No special preparation is usually needed. However, avoid taking certain medications (like steroids) that might affect eosinophil counts, and inform your doctor about any recent illnesses or allergies.
  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