Skip to content

Quantitative Immunoassay for Immunoglobulin G (IgG) Subclass Levels (Serum)

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

This test measures the specific levels of different subclasses of Immunoglobulin G (IgG), a key antibody protein in your blood. IgG subclasses play important roles in immune response and disease defense.

Quick summary

["Understanding your IgG subclass levels helps assess immune function and identify potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
44877-9
Short code
IDDM Patient Ql
Synonyms
IDDM Patient Ql
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 system function, diagnose conditions like hypogammaglobulinemia (low antibody levels), or monitor treatment responses in patients with autoimmune diseases or chronic infections.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw blood. If you’re on blood thinners, inform your healthcare provider beforehand.

What the Test Results Mean

Results show the concentration of IgG1, IgG2, IgG3, or IgG4 subclasses. Abnormal levels may indicate immune system issues, such as weakened immunity or certain autoimmune disorders.

Common Conditions Linked to IgG Subclass Testing

Conditions like recurrent infections, chronic inflammatory diseases, or immune deficiencies may prompt this test. It can also help guide treatment plans for conditions like rheumatoid arthritis or lupus.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Quantification

Frequently asked questions

What does a low IgG subclass mean?
A low IgG subclass may suggest an immune deficiency, making you more prone to infections. Your doctor may recommend additional tests or treatments to support your immune system.
How often should I get this test?
Frequency depends on your health condition. If you have a known immune disorder, your doctor may schedule follow-up tests every few months or as needed to monitor changes.
Can diet affect IgG subclass levels?
Diet can influence overall immune health, but it doesn’t directly alter IgG subclass levels. Focus on a balanced diet rich in vitamins and minerals to support immune function.
  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