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Serum Immunoassay for Immunoglobulin G (IgG) Subclass Levels (Specific to IgG1, IgG2, IgG3, IgG4)

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

This test measures the levels of specific subclasses of Immunoglobulin G (IgG), an important antibody protein in your blood. IgG subclasses help your immune system fight infections and respond to vaccines.

Quick summary

["IgG subclasses play a key role in immunity; this test helps assess immune function or identify deficiencies."]

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

Key facts at a glance

LOINC
96467-6
Short code
IP3R 1 IgG CSF Ql IF
Synonyms
IP3R 1 IgG CSF Ql IF
Category
coagulation
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82784
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of a weakened immune system, such as frequent infections, recurrent pneumonia, or unexplained infections. It could also be used to evaluate immune responses after vaccination, diagnose autoimmune conditions, or monitor treatment for conditions like lupus or rheumatoid arthritis.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for 8–12 hours before the draw, but your provider will confirm this if applicable. Bring any medications you’re currently taking, as some may affect results.

How the Test Works

A small sample of your blood is taken from a vein, usually in your arm. The blood is then analyzed using an immunoassay method to measure the concentration of each IgG subclass (IgG1, IgG2, IgG3, IgG4) separately. These results help determine if your immune system is producing these antibodies at normal levels.

What the Results Mean

Results show the concentration of each IgG subclass in your blood. Low levels of certain subclasses may indicate an immune deficiency or an autoimmune condition, while high levels could suggest overactive immune responses or certain diseases. Your healthcare provider will interpret these results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Subclass Levels

Frequently asked questions

What does my IgG subclass test result indicate?
Low levels of IgG subclasses may mean your immune system isn’t producing enough antibodies to fight infections. This can happen in conditions like Common Variable Immunodeficiency (CVID) or after certain treatments. High levels might suggest chronic inflammation, autoimmune diseases, or other immune-related disorders. Always discuss your results with your doctor, as they’ll help determine the next steps.
How often should I get this test?
The frequency depends on your health condition. If you have an immune disorder, your doctor may recommend regular monitoring. If you’re healthy, this test is usually only done if symptoms or other tests suggest an issue. Follow your provider’s advice for follow-up testing.
Does diet or medications affect IgG subclass levels?
Some medications, like steroids or certain immune-suppressing drugs, can lower IgG levels. Dietary changes, such as avoiding excessive alcohol or certain supplements, may also indirectly impact immune function. Always inform your healthcare provider about all medications or supplements you’re taking before your test.
  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