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

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

This test measures the levels of different subclasses of Immunoglobulin G (IgG), a key antibody protein in your immune system. IgG subclasses help protect against infections and regulate immune responses.

Quick summary

["IgG subclasses play a vital role in immune defense and can be checked if you have symptoms of immune-related conditions."]

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

Key facts at a glance

LOINC
40924-3
Short code
Deprecated S pneum9 IgG sp1 Ser IA-mCnc
Synonyms
Deprecated S pneum9 IgG sp1 Ser IA-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 Might You Need This Test?

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 system. It can also be part of monitoring for certain treatments.

What Does the Test Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). This test measures the concentration of these subclasses in your blood, helping identify imbalances that might indicate immune dysfunction.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it is processed to measure IgG subclass levels using immunoassay methods.

What Do the Results Mean?

Results show the concentration of each IgG subclass. Abnormal levels may suggest conditions like hypogammaglobulinemia (low IgG), immune deficiencies, or certain autoimmune diseases. Your doctor will interpret results in the context of your health history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG Subclass Levels Help Diagnose and Monitor Immune-Related Conditions

Short name

IgG Subclass Levels

Frequently asked questions

What are the normal ranges for IgG subclasses?
Normal ranges vary by lab and can’t be provided here. Your doctor will compare your results to your specific reference values and medical needs.
Can IgG subclass levels change with age?
Yes, IgG subclass levels can vary with age, especially in children, older adults, or those with chronic illnesses. Your doctor will consider these factors when evaluating your results.
How often should I get this test?
Your doctor will determine the frequency based on your symptoms, medical history, and treatment plan. Regular monitoring may be needed if you have an ongoing condition affecting your immune system.
  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