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Immunoglobulin G (IgG) Subclass Measurement (Serum)

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

This test measures the different types (subclasses) of Immunoglobulin G (IgG), a key protein in your immune system that helps fight infections. IgG subclasses vary in their roles and can be checked if you have immune-related conditions or symptoms.

Quick summary

["IgG subclasses help identify specific immune system strengths or weaknesses that may require medical attention."]

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

Key facts at a glance

LOINC
111018-8
Short code
Nuclear IgG Msmt Ser
Synonyms
Nuclear IgG 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 healthcare provider may order this test if you have symptoms like frequent infections, autoimmune diseases, or if you’re being evaluated for conditions affecting your immune response. It may also be used to monitor treatment progress in certain immune disorders.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw blood. The test is usually done in a lab and results are ready within a few days.

What the Results Mean

IgG is the most abundant antibody in your blood, but measuring its subclasses can reveal whether certain types are too high or too low. For example, low IgG1 or IgG3 might suggest immune dysfunction, while abnormal levels could indicate underlying health issues.

Common Conditions Linked to IgG Subclass Results

Changes in IgG subclass levels can signal conditions like chronic infections, certain autoimmune diseases (e.g., lupus), or immune deficiencies. Your doctor will interpret results in the context of your medical history and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

Will my IgG subclass test results affect my medications?
Possibly. If your results show an immune imbalance, your doctor may adjust medications like steroids, biologics, or immune-modulating therapies to better support your condition. Always follow your provider’s guidance.
What if my IgG subclass levels are outside normal ranges?
If your levels are abnormal, it may indicate an immune system issue that needs further evaluation. Your doctor could recommend additional tests, lifestyle changes, or treatments tailored to your specific needs.
How often should I get this test?
Frequency depends on your health status. If you have an ongoing condition (e.g., autoimmune disease), your doctor may order this test periodically to monitor changes. Otherwise, it’s usually done only when symptoms or concerns arise.
  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