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

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

This test measures the levels of specific subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is the most common antibody and plays a key role in fighting infections.

Quick summary

["Understanding your IgG subclass levels can 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
27392-0
Short code
Deprecated S pneum9 IgG Ser-mCnc
Synonyms
Deprecated S pneum9 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 of immune system issues, such as frequent infections, recurrent sinus or ear infections, or unexplained fatigue. It could also be used to monitor conditions like lupus, rheumatoid arthritis, or certain immune deficiencies.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for 8–12 hours before the test if it is part of a broader metabolic or immune evaluation. Bring any medications you’re currently taking to your appointment.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. The blood sample will be sent to a lab for analysis of IgG subclass concentrations. Results are typically available within 1–3 business days.

What the Results Mean

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4). Abnormal levels may indicate immune dysfunction, such as low IgG (hypogammaglobulinemia) or high IgG in certain subclasses. Your provider will interpret results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Subclass Levels

Frequently asked questions

What questions might you have about this test?
This test is primarily used to assess immune function and diagnose or monitor conditions affecting antibody production. It helps identify whether certain subclasses of IgG are too low or too high, which can guide treatment decisions.
How long will I need to wait for my results?
Results are usually ready within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the findings with you during your follow-up visit.
Can I eat or drink before this test?
No fasting is required for this test, but if it’s part of a broader evaluation (e.g., metabolic panel), follow your provider’s instructions. Always check with your lab or provider for specific guidelines.
  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