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

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

This test measures the different types (subclasses) of Immunoglobulin G (IgG), the most common antibody in your blood. IgG subclasses help your immune system fight infections and respond to vaccines.

Quick summary

["Understanding your IgG subclass levels can help identify immune system function or deficiencies."]

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

Key facts at a glance

LOINC
18301-2
Short code
IgG Ser Ql IFE
Synonyms
IgG Ser Ql IFE
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immunofixation
CPT
82784
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 doctor may recommend this test if you have symptoms like frequent infections, poor wound healing, or if you’ve had a recent vaccination. It could also be part of an evaluation for autoimmune diseases or immune disorders.

What to Expect Before the Test

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

What the Test Results Mean

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Lower-than-expected levels in any subclass may indicate an immune deficiency or other health issue. Higher-than-expected levels might suggest chronic infections or certain immune disorders.

Common Conditions Linked to IgG Subclass Results

Abnormal IgG subclass levels can signal conditions like common variable immunodeficiency (CVID), HIV/AIDS, or certain autoimmune diseases. Your doctor will interpret results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG subclass testing is critical for diagnosing or monitoring immune-related conditions. Low levels of specific subclasses can point to weakened immune responses, while elevated levels may indicate chronic inflammation or immune activation. This test helps guide treatment plans for immune disorders or infections.

Short name

IgG Subclass Levels

Frequently asked questions

What does a low IgG subclass mean?
A low IgG subclass may suggest an immune system that struggles to produce enough antibodies to fight infections. This could be due to a genetic disorder, autoimmune disease, or other health conditions affecting your immune function. Your doctor may recommend further testing or treatments to support your immune response.
How often should I get this test?
The frequency depends on your health condition and doctor’s recommendations. If you have an immune disorder, your doctor may order this test regularly to monitor changes in your IgG levels. If you’re healthy, it’s usually not routine unless symptoms arise.
Can diet or supplements affect IgG subclass levels?
While diet and supplements can support overall immune health, they don’t directly alter IgG subclass levels. However, maintaining a balanced diet rich in vitamins (like vitamin D, zinc) and staying hydrated can help support your immune system’s 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