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Eosinophil count in serum/plasma (mass concentration)

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

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

Quick summary

["Eosinophil levels can help diagnose or monitor conditions involving allergies, infections, or inflammatory diseases."]

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

Key facts at a glance

LOINC
16819-5
Short code
E histolyt Ab Ser IF-aCnc
Synonyms
E histolyt Ab Ser IF-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 if you have symptoms like persistent itching, skin rashes, asthma, or unexplained weight loss. It may also be used to check for conditions such as parasitic infections, certain cancers, or autoimmune disorders.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The sample is then processed to count eosinophils in your serum or plasma using a specialized laboratory technique.

What Are Common Uses?

Eosinophil counts help identify allergic reactions, parasitic infections, and conditions like asthma, eosinophilic esophagitis, or certain types of leukemia.

What Are Possible Results?

Results are typically reported as a count of eosinophils per microliter of blood. Elevated levels may indicate allergies, infections, or inflammatory conditions, while very low levels might suggest immune suppression or other health issues.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum/plasma eosinophil count

Frequently asked questions

What does an elevated eosinophil count mean?
An elevated eosinophil count may suggest conditions like allergies, asthma, parasitic infections, or certain inflammatory diseases. Your doctor will consider your symptoms and medical history to determine the cause.
What does a normal or low eosinophil count mean?
A normal eosinophil count usually indicates a healthy immune response. Low levels might be due to immune suppression, certain medications, or underlying health conditions. Discuss your results with your doctor for personalized insights.
Can diet or lifestyle affect eosinophil levels?
Diet and lifestyle factors can sometimes influence white blood cell counts, including eosinophils. Avoiding known allergens, managing stress, and maintaining a balanced diet may support overall immune health, but results depend on the underlying condition being tested.
  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