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Immunoglobulin G (IgG) Subclass Measurement (Serum/Plasma Mass Concentration)

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

This test measures the specific amounts of different types (subclasses) of Immunoglobulin G (IgG), a key antibody protein in your blood. IgG helps fight infections and is important for long-term immunity.

Quick summary

["IgG subclasses help identify immune system function and potential deficiencies or disorders."]

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

Key facts at a glance

LOINC
24433-5
Short code
IgG Equine Ser-mCnc
Synonyms
IgG Equine Ser-mCnc
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

What Does This Test Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with distinct roles in immunity. This test quantifies the concentration of these subclasses in your serum or plasma. Variations can indicate immune system issues, such as infections, autoimmune diseases, or immune deficiencies.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms like frequent infections, unexplained fatigue, or if you’re being evaluated for conditions like common variable immunodeficiency (CVID), autoimmune disorders, or other immune-related problems.

How Is the Test Performed?

A blood sample is drawn from a vein, typically in your arm. The blood is then processed to separate serum or plasma, which is analyzed using a specialized immunoassay method to measure IgG subclass concentrations.

What Are Common Results and Next Steps?

Results may show elevated or reduced levels of specific IgG subclasses compared to expected ranges. Abnormal findings often prompt further testing or evaluation by an immunologist or specialist to determine the underlying cause.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

Why do IgG subclass levels matter in my health?
IgG subclasses support different aspects of immunity, such as opsonization (tagging pathogens for destruction), neutralization of viruses, and complement activation. Low levels of certain subclasses may suggest immune dysfunction, while high levels could indicate chronic inflammation or other conditions.
What if my test results are abnormal?
If your IgG subclass levels are outside normal ranges, your healthcare provider may recommend additional tests, such as antibody response to vaccines, immune function studies, or genetic evaluations to identify the cause of your symptoms.
How often should I get this test?
The frequency depends on your medical condition. If you have an immune disorder, your provider may recommend regular monitoring. Otherwise, this test is usually ordered as needed for specific symptoms or diagnostic purposes.
  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