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Immunoglobulin G (IgG) Subclass Measurement (Serum/Plasma)

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

This test measures the levels of different subclasses of Immunoglobulin G (IgG), a key antibody protein in your immune system. IgG subclasses help protect against infections and regulate immune responses.

Quick summary

["IgG subclasses play a vital role in your immune defense and can be checked for various health conditions."]

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

Key facts at a glance

LOINC
104272-0
Short code
IgH+IgK gene status Spec
Synonyms
IgH+IgK gene status Spec
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
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 Is This Test Done?

Doctors may order IgG subclass testing to evaluate immune function, diagnose conditions like hypogammaglobulinemia (low IgG levels), or assess responses to treatments for autoimmune diseases or infections. It can also help identify specific antibody deficiencies that may affect your ability to fight certain pathogens.

What Does It Measure?

IgG is divided into four subclasses (IgG1, IgG2, IgG3, and IgG4), each with distinct roles. This test measures the concentration of these subclasses in your blood serum or plasma, helping to identify imbalances that might indicate immune system issues.

Sample Preparation and Testing Process

A blood sample is drawn, typically from a vein in your arm. The blood is then processed to separate serum or plasma for testing. The IgG subclasses are analyzed using a specialized immunoassay method, which detects and quantifies each subclass separately.

What Are Normal Results?

There are no specific numeric reference ranges provided here since they can vary by lab and test method. Your results will be compared to your lab’s standards, and your healthcare provider will interpret them in the context of your overall health and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What causes IgG subclass levels to be abnormal?
IgG subclass abnormalities can result from genetic disorders, chronic illnesses (like HIV or hepatitis), long-term use of certain medications, or autoimmune diseases. They may also appear in people with weakened immune systems due to aging or treatments like chemotherapy.
How often should I get this test?
The frequency of this test depends on your medical condition and treatment plan. If you have a known immune disorder, your doctor may recommend periodic testing to monitor changes in your IgG subclass levels. Follow-up testing is often scheduled every few months or as needed based on your symptoms and lab results.
Can lifestyle changes affect IgG subclass levels?
While diet, exercise, and stress management can support overall immune health, they may not directly alter IgG subclass levels. However, maintaining a balanced diet rich in vitamins (like vitamin D and B12) and staying hydrated can help support immune function, which may indirectly benefit your test results.
  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