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

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

This test measures the different types (subclasses) of Immunoglobulin G (IgG), a key antibody protein in your blood that helps fight infections and diseases. IgG subclasses play distinct roles in immunity.

Quick summary

["Understanding your IgG subclass levels can help identify immune system imbalances or deficiencies."]

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

Key facts at a glance

LOINC
109816-9
Short code
IgLON5 IgG Msmt CSF
Synonyms
IgLON5 IgG Msmt CSF
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What IgG Subclasses Are Measured?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with unique functions. This test typically assesses concentrations of these subclasses, though exact methods may vary. IgG1 and IgG2 are most commonly evaluated in routine testing.

Why Might This Test Be Ordered?

Your healthcare provider may order this test if you have symptoms of immune system issues, such as frequent infections, autoimmune diseases, or conditions affecting antibody production. It can also be part of evaluating immune response to vaccines or treatments.

Sample Collection and Preparation

This test requires a blood sample drawn from a vein, usually in a clinic or lab. The blood is processed into serum or plasma for analysis. No special preparation is needed, but fasting may be advised depending on the clinical context.

What Does the Test Result Mean?

Results show the relative or absolute levels of IgG subclasses, often expressed as a ratio or percentage of total IgG. Abnormal levels may indicate immune dysfunction, such as hypogammaglobulinemia (low IgG) or selective IgG subclass deficiencies.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What causes abnormal IgG subclass levels?
Abnormal IgG subclass levels can result from genetic disorders, chronic illnesses (e.g., lupus), immune system disorders, or treatments that suppress the immune response. Rarely, certain medications or infections may also affect these levels.
How often should I get this test?
The frequency depends on your symptoms and medical history. Your doctor may recommend follow-up testing if you have a known immune disorder or if your levels are already abnormal. Regular monitoring may be needed for chronic conditions.
Can lifestyle changes affect IgG subclass levels?
While diet and lifestyle factors may influence overall immune function, IgG subclass levels are primarily determined by genetic and immune system factors. However, maintaining a balanced diet rich in vitamins (e.g., vitamin D, B12) and staying hydrated may support overall immune health.
  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