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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 blood that helps fight infections and diseases.

Quick summary

["IgG subclasses help identify immune system function and potential deficiencies or disorders."]

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

Key facts at a glance

LOINC
86044-5
Short code
S pneum Da 2 IgG 2:1 Ser-Rto
Synonyms
S pneum Da 2 IgG 2:1 Ser-Rto
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 this test to evaluate immune function, diagnose conditions like hypogammaglobulinemia (low IgG), or assess responses to treatments for immune-related disorders. It can also help monitor immune responses in chronic illnesses or after certain therapies.

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 the most abundant antibody in your blood, but its subclasses (IgG1, IgG2, IgG3, IgG4) have different roles. Abnormal levels may indicate immune system issues, such as poor infection defense or autoimmune conditions.

Common Conditions Linked to IgG Subclass Results

Low levels of certain IgG subclasses can signal immune deficiencies, recurrent infections, or chronic inflammatory diseases. High levels may be seen in certain autoimmune disorders or chronic infections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What does a low IgG subclass mean?
A low IgG subclass may suggest an immune system that struggles to produce enough antibodies, increasing your risk of infections. This could be due to a genetic disorder, treatment side effects, or chronic illness.
What if my IgG subclass results are normal?
Normal results mean your immune system is likely producing adequate IgG antibodies, but further testing may still be needed if you have symptoms like frequent infections or unexplained fatigue. Your doctor will guide next steps.
Can diet or supplements affect IgG subclass levels?
While diet and supplements can support overall immune health, they don’t directly alter IgG subclass levels. Focus on a balanced diet rich in vitamins and minerals, and discuss any concerns with your healthcare provider.
  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