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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 bacteria, viruses, and toxins.

Quick summary

["IgG subclasses play a vital role in immune defense and can be important for diagnosing and managing certain conditions."]

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

Key facts at a glance

LOINC
2465-3
Short code
IgG SerPl-mCnc
Synonyms
IgG SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 healthcare provider may order this test if you have symptoms of immune system issues, such as frequent infections, unexplained fatigue, or autoimmune diseases. It may also be used to monitor treatment responses in conditions like chronic infections, immune deficiencies, or certain cancers.

What to Expect Before the Test

No special preparation is usually needed. You may have a blood sample drawn from a vein in your arm. If you’re on blood thinners, inform your provider beforehand.

What the Results Mean

IgG subclasses are measured in mass concentration units. Abnormal levels may suggest immune system disorders, infections, or other health concerns. Your results will be interpreted by your healthcare provider in the context of your medical history and symptoms.

Common Conditions Affecting IgG Subclass Levels

Low IgG subclass levels might indicate immune deficiencies, such as common variable immunodeficiency (CVID). High levels could be seen in chronic infections, autoimmune diseases, or certain inflammatory conditions. Always discuss your results with your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG subclass testing is critical for diagnosing and managing conditions where specific antibody responses are impaired or excessive. For example, low IgG subclasses may point to a weakened immune response, while elevated levels could indicate chronic inflammation or immune activation. Early identification helps tailor treatment strategies.

Short name

IgG Subclass Levels

Frequently asked questions

What does an abnormal IgG subclass result mean?
An abnormal result doesn’t have a single cause. It could be linked to an immune disorder, infection, or other health conditions. Your doctor will review your test results alongside your medical history and symptoms to determine the next steps.
How often should I get this test?
The frequency depends on your health condition and treatment plan. If you have a chronic condition like CVID or another immune-related illness, your doctor may recommend regular monitoring. Otherwise, this test is usually ordered as needed for specific concerns.
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 lifestyle can help support your immune system’s 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