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Immunoglobulin G (IgG) Subclass Measurement (Serum)

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

This test measures different types of IgG antibodies in your blood, which play a key role in fighting infections and supporting immune function.

Quick summary

["IgG subclasses help identify specific immune responses and potential deficiencies."]

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

Key facts at a glance

LOINC
109987-8
Short code
IgD Msmt Ser
Synonyms
IgD 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
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 they suspect an immune system issue. It can also be used to monitor certain treatments or conditions affecting antibody production.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw blood. It usually takes a few minutes, and you may feel a brief pinch. If you’re on blood thinners, let your provider know before the test.

What the Test Results Mean

IgG is the most abundant antibody in your blood, but it’s divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Each subclass has a different role in immunity. Abnormal levels may indicate immune system problems, such as low resistance to infections or autoimmune diseases.

Common Conditions Linked to IgG Subclass Results

Low levels of certain IgG subclasses can be linked to conditions like recurrent infections, severe allergic reactions, or certain autoimmune disorders. High levels may sometimes suggest overactive immune responses or certain immune-related conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG subclasses are important for diagnosing and managing conditions like chronic infections, immunodeficiency disorders, or autoimmune diseases. They help tailor treatments to address specific immune weaknesses or overactivations.

Short name

IgG Subclass Test

Frequently asked questions

What does a low IgG subclass mean in my results?
A low IgG subclass may indicate an immune system that struggles to produce enough antibodies to fight infections effectively. This could be due to genetic disorders, certain medications, or chronic illnesses. Your provider may recommend further testing or treatments to support your immune function.
How often should I get this test?
The frequency depends on your health condition and treatment plan. If you have a known immunodeficiency or autoimmune disease, your provider may order this test regularly. Otherwise, it’s usually only done if symptoms or other test results suggest a need.
Can diet or supplements affect IgG subclass levels?
While diet and supplements can influence overall immune health, they don’t directly affect IgG subclass levels. However, maintaining a balanced diet rich in vitamins and minerals supports a healthy immune system, which may indirectly benefit antibody production.
  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