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Serum or Plasma Immunoassay for Immunoglobulin G (IgG) Subclass Quantification (Subclasses G1, G2, G3, G4)

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

This test measures the specific types (subclasses) of Immunoglobulin G (IgG), a key antibody protein in your immune system, in your blood.

Quick summary

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

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

Key facts at a glance

LOINC
111038-6
Short code
LCMV IgG Msmt Ser
Synonyms
LCMV IgG Msmt Ser
Category
chemistry
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 can also help monitor treatment responses in certain diseases.

What to Expect Before the Test

No special preparation is needed. You may have a blood draw, and the sample will be sent to a lab for analysis. If you’re on blood-thinning medication, let your provider know before the test.

What the Results Mean

IgG is divided into four subclasses (G1, G2, G3, G4), each with different roles in immune defense. Abnormal levels may suggest immune system issues, such as low immunity or overactivity.

Common Conditions Linked to IgG Subclass Results

Low levels of certain IgG subclasses might indicate conditions like common variable immunodeficiency (CVID) or other immune deficiencies. High levels could be linked to autoimmune diseases 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 indicate an immune system that struggles to produce enough antibodies, increasing your risk of infections. This could be due to genetic disorders, chronic illnesses, or certain medications.
What does a high IgG subclass mean?
High IgG subclass levels may suggest an overactive immune response, such as in autoimmune diseases or chronic infections. Your provider will discuss findings in the context of your symptoms and medical history.
How often should I get this test?
Your provider will determine the frequency based on your health needs, symptoms, or treatment plan. Regular monitoring may be needed if you have an ongoing condition affecting IgG levels.
  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