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Immunoglobulin G (IgG) Subclass Measurement (Serum)

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; abnormal levels may indicate immune system issues."]

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

Key facts at a glance

LOINC
31183-7
Short code
Deprecated S pneum5 IgG Ser-mCnc
Synonyms
Deprecated S pneum5 IgG Ser-mCnc
Category
coagulation
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 recommend this test if you have symptoms like frequent infections, autoimmune diseases, or if you’re being evaluated for conditions affecting your immune system. It could also be part of a broader evaluation for certain blood disorders or after receiving immune-modifying treatments.

What to Expect Before the Test

No special preparation is usually needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. If you’re nervous, let your healthcare provider know—they can help make it more comfortable.

What the Results Mean

IgG subclasses are measured in mass concentration units (e.g., grams per liter). While reference ranges vary by lab, lower or higher than expected levels may signal potential immune dysfunction, such as inadequate antibody production or overactivity.

Common Conditions Linked to IgG Subclass Results

Abnormal IgG subclass results may be linked to conditions like hypogammaglobulinemia (low IgG), hyper-IgG syndromes, or autoimmune diseases. Your provider will discuss findings in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What does a low IgG subclass result mean?
A low IgG subclass result may indicate a weakened immune system, potentially due to genetic disorders, chronic illnesses, or treatments that suppress immune function. Your provider will review your medical history and other test results to determine the cause and next steps.
How often should I get this test?
The frequency depends on your health condition. If you have a known immune disorder, your provider may recommend regular monitoring. For routine check-ups or after treatment, they’ll determine the best timing based on your individual needs.
Can diet or supplements affect IgG subclass levels?
While diet and supplements may support overall immune health, they don’t directly alter IgG subclass levels. Focus on a balanced diet rich in vitamins and minerals, and always discuss supplements with your provider before use.
  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