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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 in your immune system. IgG subclasses help protect against bacteria, viruses, and toxins.

Quick summary

["Understanding your IgG subclass levels can help identify immune system strengths or weaknesses."]

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

Key facts at a glance

LOINC
53260-6
Short code
GBM Ab Ser Ql IF
Synonyms
GBM Ab Ser Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 IgG Subclasses Matter

IgG is the most abundant antibody in your blood and plays a critical role in defending against infections. It’s divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with distinct functions. Low levels of certain subclasses may indicate immune deficiencies or chronic illnesses.

What to Expect During Testing

A blood sample is drawn from a vein, usually in your arm. The blood is sent to a lab where it’s analyzed to determine the concentration of each IgG subclass. Results are typically available within a few days.

Common Reasons for Testing

Doctors may order this test if you have recurrent infections, autoimmune diseases, or if you’re suspected of having an immune disorder. It can also be part of a broader evaluation for conditions like lupus, rheumatoid arthritis, or certain cancers.

What Your Results Mean

Results are reported as concentrations of each subclass, though exact reference ranges can vary by lab. Abnormal levels may suggest immune dysfunction, requiring further medical evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

How often do I need this test?
IgG subclass testing is usually done as part of a specific medical evaluation, such as diagnosing an immune disorder. Your doctor will determine if follow-up testing is needed based on your symptoms and results.
What are normal IgG subclass levels?
There are no universally standardized reference ranges for IgG subclasses alone. Instead, results are often interpreted in the context of your overall health and clinical picture. Your doctor will discuss what your results mean for you.
Can low or high IgG subclass levels be treated?
Yes, depending on the cause. Low IgG levels may be managed with immune-boosting therapies, such as immunoglobulin replacement therapy. High levels may not require treatment unless they’re linked to a specific condition like autoimmune disease.
  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