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Immunoglobulin G (IgG) Subclass Quantification (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 blood that helps fight infections and diseases.

Quick summary

["IgG subclasses help identify specific immune responses and potential deficiencies."]

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

Key facts at a glance

LOINC
107196-8
Short code
IgK gene Tube B Spec
Synonyms
IgK gene Tube B Spec
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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 recommend this test if you have symptoms like frequent infections, autoimmune conditions, or if you’re being evaluated for immune system disorders. It can also help diagnose or monitor conditions affecting antibody production, such as certain immune deficiencies or chronic infections.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re nervous, let your healthcare provider know—they can help make it more comfortable.

What the Results Mean

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Abnormal levels of any subclass can indicate immune system issues, such as reduced ability to fight certain infections or autoimmune reactions. Your results will be compared to standard ranges for your age and health status.

Common Conditions Linked to IgG Subclass Results

Low levels of certain IgG subclasses may suggest immune deficiencies (e.g., selective IgA deficiency, common variable immunodeficiency). High levels could be seen in chronic infections, autoimmune diseases, or certain cancers. Your provider will discuss findings in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What does a low IgG subclass mean?
A low IgG subclass may mean your immune system isn’t producing enough of that particular antibody to protect against certain infections or diseases. This could be due to an underlying immune deficiency, aging, or certain medications. Your provider will review your symptoms and other test results to determine the cause and next steps.
How often should I get this test?
The frequency depends on your health condition. If you have an immune disorder, your provider may recommend regular monitoring. If this test is part of a routine check, they’ll let you know how often it’s needed. Follow their advice to stay informed about your immune health.
Can lifestyle changes affect IgG subclass levels?
While diet, exercise, and stress management support overall immune function, they don’t directly alter IgG subclass levels. However, maintaining a balanced diet rich in vitamins (like vitamin D and B12) and staying hydrated can support immune health. Always discuss any changes with your healthcare provider.
  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