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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 protein in your immune system. IgG subclasses help fight infections and support immune memory.

Quick summary

["IgG subclasses play a vital role in your body’s immune defense, and their levels can be checked for various health conditions."]

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

Key facts at a glance

LOINC
30561-5
Short code
Deprecated S pneum6 IgG Ser IA-mCnc
Synonyms
Deprecated S pneum6 IgG 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 This Test Is Done

Doctors may order this test to evaluate immune function, diagnose or monitor conditions like immunodeficiency, autoimmune diseases, or certain infections. It can also help assess responses to treatments or identify issues with antibody production.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. The test is quick and typically done in a clinic or lab setting.

What the Results Mean

IgG is the most abundant antibody in your blood, but it’s divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Abnormal levels of any subclass can indicate problems with immune response, such as low production (immunodeficiency) or excessive presence (autoimmune disorders).

Common Conditions Monitored

This test helps diagnose or manage conditions like common variable immunodeficiency (CVID), HIV/AIDS, certain autoimmune diseases (e.g., lupus), or infections where antibody levels may be affected.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What causes IgG subclass levels to change?
IgG subclass levels can be influenced by immune system disorders (e.g., immunodeficiency), chronic infections, autoimmune diseases, or certain medications. Aging, malnutrition, or underlying health conditions may also affect these levels.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on lab processing times. Your healthcare provider will discuss the findings with you during your follow-up visit.
Can diet or lifestyle affect IgG subclass test results?
While diet and lifestyle factors like stress or infections can impact overall immune function, they generally do not directly alter IgG subclass levels. However, maintaining a balanced diet and good health supports 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