Skip to content

Immunoglobulin G (IgG) Subclass Measurement (Serum)

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

This test measures the levels of specific 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

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

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

Key facts at a glance

LOINC
22541-7
Short code
Deprecated S pneum 1 IgG Ser-aCnc
Synonyms
Deprecated S pneum 1 IgG Ser-aCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 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-related disorders. It may also be used to monitor treatment responses in certain conditions.

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 lab setting.

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 low antibody production, overactivity, or specific immune deficiencies.

Common Conditions Monitored

IgG subclass testing is often used to diagnose or monitor conditions like common variable immunodeficiency, autoimmune diseases (e.g., rheumatoid arthritis), or infections where antibody responses are impaired.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Testing

Frequently asked questions

What does IgG subclass testing involve?
This test measures the precise amounts of each IgG subclass (IgG1, IgG2, IgG3, IgG4) in your blood serum. It helps assess immune function by identifying imbalances that may not be detected by general IgG testing alone.
How often should I get this test?
The frequency depends on your medical condition and provider’s recommendations. Some patients with chronic immune disorders may need testing every few months, while others may only need it once.
Can lifestyle changes affect IgG subclass levels?
While diet, stress, and infections can influence immune function broadly, IgG subclass levels are primarily determined by your body’s immune response. Your provider will guide any lifestyle adjustments based on your specific results.
  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