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Eosinophil count (serum-based differential blood analysis)

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

This test measures the number of eosinophils, a type of white blood cell, often analyzed as part of a complete blood count (CBC) or blood differential.

Quick summary

["Eosinophils help identify certain immune or inflammatory responses in your blood."]

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

Key facts at a glance

LOINC
109357-4
Short code
ECV IgM Msmt Ser
Synonyms
ECV IgM Msmt Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 This Test Might Be Ordered

Your doctor may request this test to diagnose or monitor conditions like allergies, asthma, parasitic infections, or certain autoimmune diseases. It can also help assess reactions to medications or identify hidden causes of unexplained symptoms.

What to Expect Before the Test

No special preparation is needed. You may have a simple blood draw, often done in a doctor’s office or lab. If you’re on blood thinners, let your provider know beforehand.

What the Results Mean

Results are usually reported as a count of eosinophils per microliter of blood. Elevated levels may signal allergies, infections, or other immune-related conditions, while very low levels could indicate certain blood disorders or chronic illnesses.

Common Conditions Monitored

Eosinophil counts are often checked alongside other blood tests to guide treatment for allergies, asthma, parasitic infections, or conditions like eosinophilic esophagitis or certain cancers.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

What causes eosinophils to rise in the blood?
Elevated eosinophil counts can result from allergies, asthma, parasitic infections, certain cancers (like Hodgkin lymphoma), or autoimmune diseases. Stress, medications, or even certain foods may also trigger temporary spikes.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss them with you during your follow-up visit.
Can I eat or drink before this test?
No special diet or fasting is required for this test, but always follow your healthcare provider’s instructions for any specific preparations related to your blood draw.
  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