Skip to content

Serum or plasma mass concentration of immunoglobulin G (IgG) subclasses (IgG1, IgG2, IgG3, IgG4)

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

This test measures the specific amounts of different types of Immunoglobulin G (IgG), a key antibody protein in your blood. IgG helps fight infections and is important for long-term immunity.

Quick summary

["IgG subclasses help diagnose immune system disorders and guide treatment for conditions like infections, autoimmune diseases, or immune deficiencies."]

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

Key facts at a glance

LOINC
98051-6
Short code
M canis IgE Qn
Synonyms
M canis IgE Qn
Category
chemistry
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

What Does This Test Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with a distinct role in immunity. This test quantifies each subclass’s concentration in your blood, often measured in milligrams per deciliter (mg/dL). The results help identify imbalances that may indicate immune system issues.

Why Might You Need This Test?

Doctors may order IgG subclass testing if you have symptoms like frequent infections, unusual fatigue, or autoimmune conditions. It can also help monitor treatments for immune-related disorders or check for immune deficiencies.

Common Conditions Linked to IgG Subclass Testing

Low levels of certain IgG subclasses may suggest weakened immunity, while high levels could indicate overactive immune responses or certain diseases. For example, low IgG2 is often linked to recurrent sinus or respiratory infections.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then processed to separate serum or plasma, where IgG subclasses are measured using specialized laboratory techniques, such as nephelometry or immunoassay.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG subclass levels

Frequently asked questions

What Are Normal Results?
Normal results vary by lab and IgG subclass. Your results will be compared to reference ranges specific to your age, health, and medical history. Your doctor will interpret the results in the context of your overall health.
Can I Prepare for This Test?
No special preparation is needed, but avoid heavy meals before the blood draw. If you’re on medications, let your doctor know—some may affect test results.
How Long Does It Take to Get Results?
Results are typically available within 1–3 business days, depending on your lab. Your doctor will discuss the findings with you during your follow-up visit.
  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