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Immunoglobulin G (IgG) Subclass Measurement (Serum)

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; abnormal levels may indicate immune system issues or other health concerns."]

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

Key facts at a glance

LOINC
86040-3
Short code
S pneum Da 2 IgG sp1 Ser IA-mCnc
Synonyms
S pneum Da 2 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

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 to assess immune function, response to vaccines, or potential deficiencies.

Why Might You Need This Test?

Doctors may order this test if you have symptoms of immune disorders (e.g., frequent infections, autoimmune conditions), suspected antibody deficiencies, or if you’re being evaluated for conditions like hypogammaglobulinemia or certain infections.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The blood is processed to separate serum (the liquid part without clotting factors) for testing. This sample is then analyzed using an immunoassay method to measure IgG subclass concentrations.

Common Reasons for Testing

This test is often used to diagnose or monitor conditions such as primary immunodeficiency, chronic infections, or immune-related diseases. It can also help evaluate vaccine responses or guide treatment plans for patients with antibody-related disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What Are Normal Results?
Normal results vary by lab and individual, but low or high levels of specific IgG subclasses may indicate immune system imbalances. For example, low IgG2 levels might suggest difficulty fighting certain bacteria, while high IgG4 could be linked to allergic reactions or autoimmune conditions. Always discuss results with your healthcare provider.
How Do IgG Subclass Levels Affect My Health?
Abnormal IgG subclass levels can signal immune dysfunction. Low IgG subclasses may increase susceptibility to infections, while elevated levels in certain subclasses (e.g., IgG4) could be associated with autoimmune diseases or allergies. Your doctor will interpret results in the context of your symptoms and medical history.
What Conditions Might Be Diagnosed or Monitored With This Test?
This test helps diagnose or monitor conditions like common variable immunodeficiency, chronic infections (e.g., mycobacterial), or autoimmune diseases (e.g., rheumatoid arthritis). It may also assess immune responses to vaccines or guide treatment for patients with antibody deficiencies.
  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