Eosinophil count (serum/plasma-based differential blood cell count)
This test measures the number of eosinophils, a type of white blood cell that helps fight certain infections and allergic reactions.
["Eosinophils help your body respond to parasites, allergies, and some chronic conditions."]
Key facts at a glance
- LOINC
- 102959-4
- Short code
- Helminthosporium IgG RAST
- Synonyms
- Helminthosporium IgG RAST
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- rast
- CPT
- 84484
- SNOMED
- 302774002
- 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
What Are Eosinophils?
Eosinophils are a type of immune cell that play a role in defending against parasites, managing allergic responses, and protecting against certain infections. They are part of your body’s white blood cell count and can increase in response to inflammation, allergies, or parasitic infections.
Why Might Your Doctor Order This Test?
Your doctor may check eosinophil levels if you have symptoms like persistent itching, skin rashes, digestive issues, or unexplained fatigue. It can also help diagnose conditions such as allergic reactions, parasitic infections, or certain autoimmune diseases.
Common Conditions Affecting Eosinophil Levels
High eosinophil counts may suggest conditions like asthma, allergies, parasitic infections, or certain cancers (e.g., lymphoma). Low levels might indicate immune suppression or other underlying health issues.
How Is This Test Done?
A small blood sample is drawn from your arm, and the lab analyzes it under a microscope to count eosinophils. The result is expressed as a percentage or absolute count of eosinophils in your blood.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated eosinophil counts can indicate allergic reactions, parasitic infections, certain lung diseases (like eosinophilic pneumonia), or conditions like hypereosinophilic syndrome. Low levels may suggest immune dysfunction or other systemic issues.
Short name
Eosinophil count
Frequently asked questions
What Does an Abnormal Result Mean?
How Often Should I Get This Test?
Can Lifestyle Changes Affect Eosinophil Levels?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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 17, 2026. · Read our editorial policy