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Total Immunoglobulin G (IgG) Subclass Measurement (Serum)

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

This test measures the levels of different types (subclasses) of Immunoglobulin G (IgG), a key protein in your immune system. IgG helps fight infections and provides long-term immunity.

Quick summary

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

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

Key facts at a glance

LOINC
110117-9
Short code
TIF1-gamma Ab Msmt Ser
Synonyms
TIF1-gamma Ab 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, recurrent sinus or ear infections, or if you have a suspected immune disorder. It could also be part of a broader evaluation for conditions like common variable immunodeficiency (CVID) or other immune system issues.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into your arm or hand to draw blood. If you’re on blood thinners, let your provider know before the test.

What the Test Results Mean

Results show the concentration of IgG subclasses (IgG1, IgG2, IgG3, IgG4) in your blood. Abnormal levels may indicate immune system problems, such as low immunity or overactive immune responses.

Common Conditions Linked to IgG Subclass Results

Low levels of certain IgG subclasses might suggest conditions like CVID, HIV, 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 Test

Frequently asked questions

What does a low or high IgG subclass mean in my results?
A low IgG subclass may indicate an immune deficiency, which can make you more prone to infections. A high IgG subclass could suggest an overactive immune response or chronic inflammation. Always discuss your results with your healthcare provider for personalized interpretation.
Do IgG subclass levels change with age?
Yes, IgG subclass levels can vary with age. Infants and young children may have different baseline levels compared to adults. If you’re concerned about age-related changes, talk to your doctor about how your results fit into your overall health picture.
Can lifestyle or diet affect IgG subclass test results?
While diet and lifestyle factors may influence overall immune function, IgG subclass test results are primarily about the concentration of specific proteins in your blood. Your healthcare provider will focus on clinical context rather than diet alone when interpreting these 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