Skip to content

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

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

["IgG subclasses play vital roles in immunity and can be checked if you have recurrent infections or immune-related conditions."]

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

Key facts at a glance

LOINC
27405-0
Short code
Deprecated S pneum56 IgG Ser-mCnc
Synonyms
Deprecated S pneum56 IgG Ser-mCnc
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 Is Done

Doctors may order IgG subclass testing if you have symptoms like frequent infections, autoimmune diseases, or conditions affecting antibody function. It helps identify which IgG subclasses are low or high, guiding treatment decisions.

What to Expect Before the Test

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

What the Results Mean

Results show the concentration of IgG1, IgG2, IgG3, or IgG4 in your blood. Abnormal levels may indicate immune system issues, such as hypogammaglobulinemia or certain autoimmune disorders.

Common Conditions Linked to IgG Subclass Testing

IgG subclass testing is often used in diagnosing or monitoring conditions like chronic infections, severe combined immunodeficiency (SCID), or autoimmune diseases like lupus or rheumatoid arthritis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG subclasses are part of your immune defense, and their levels can reflect how well your immune system is functioning. Low levels may require immune-boosting therapies or treatments targeting specific antibodies.

Short name

IgG Subclass Levels

Frequently asked questions

What does a low IgG subclass mean?
A low IgG subclass could suggest a weakened immune response, potentially due to genetic disorders, chronic illness, or treatments that suppress antibody production. It may require further evaluation to determine the cause and appropriate interventions.
How often should I get this test?
The frequency depends on your health condition. If you have a known immune disorder, your doctor may recommend regular monitoring. Otherwise, this test is usually done only when symptoms or concerns arise.
Can diet or supplements affect IgG subclass levels?
Dietary changes or supplements may indirectly support immune health, but they don’t directly alter IgG subclass levels. Focus on a balanced diet and consult your doctor before starting new supplements.
  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