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IgE (Immunoglobulin E) in Serum or Plasma

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of Immunoglobulin E (IgE), a type of antibody your body produces in response to allergens or infections.

Quick summary

["IgE helps identify allergies or immune reactions but isn’t used to diagnose specific causes alone."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
102287-0
Short code
Whole Egg IgE RAST
Synonyms
Whole Egg IgE 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 IgE Measures

IgE is part of your immune system’s defense against certain triggers like pollen, dust, or food. High levels may signal allergies, asthma, or other allergic conditions. Very low levels might suggest a weakened immune response to allergens.

Common Uses

Doctors may order this test to diagnose allergies, check for allergic reactions, or evaluate immune function in conditions like atopic dermatitis or certain infections.

How the Test Works

Blood is drawn and sent to a lab where it’s analyzed using an immunoassay method to detect IgE antibodies. Results help determine if your immune system is overreacting to allergens or responding to infections.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about any medications (like antihistamines) or recent illnesses that could affect results.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgE Level

Frequently asked questions

Why might my IgE test be ordered?
Your doctor may recommend this test if you have symptoms like sneezing, itching, or skin reactions, or if you’re being evaluated for conditions like food allergies, eczema, or chronic asthma.
What do my IgE results mean?
Results alone don’t diagnose a specific condition. Your doctor will compare them to your symptoms and medical history to determine next steps, such as allergy testing or treatment adjustments.
Can IgE levels change over time?
Yes, IgE levels can fluctuate due to allergens, infections, or treatments. If you’ve had recent changes in symptoms or medications, mention them to your provider when reviewing results.
  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 17, 2026. · Read our editorial policy