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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 infections and regulate immune responses.

Quick summary

["IgG subclasses play a vital role in your body’s defense system and can be checked if you have symptoms of immune disorders or infections."]

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

Key facts at a glance

LOINC
81205-7
Short code
Cryo IgA + IgG + IgM + C3 Pnl Ser
Synonyms
Cryo IgA + IgG + IgM + C3 Pnl Ser
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 recommend this test if you have symptoms like frequent infections, autoimmune conditions, or if you’re being evaluated for conditions such as hypogammaglobulinemia (low IgG levels) or certain immune deficiencies. It may also be part of monitoring for diseases like multiple sclerosis or certain cancers.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Bring any medications you’re taking, as some may affect results.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but the procedure is quick and usually painless. The blood sample is then sent to a lab for analysis using immunoassay methods to detect IgG subclass concentrations.

What the Results Mean

Results show the levels of IgG1, IgG2, IgG3, and IgG4 subclasses. Abnormal levels may indicate immune system issues, such as overactive or underactive immune responses, or certain genetic disorders. Your provider will discuss these findings with you in the context of your health history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What questions might you have about this test?
IgG subclasses are part of your body’s immune defense, and their levels can provide clues about how well your immune system is functioning. For example, low IgG2 levels might be linked to recurrent sinus or respiratory infections, while elevated IgG3 could be seen in certain autoimmune conditions or chronic infections. Your provider will interpret results alongside your symptoms and medical history to guide next steps.
How long will I need to wait for my results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will contact you to discuss the findings once they are ready. If you have urgent concerns, ask your provider about next steps during your appointment.
Can I eat or drink before this test?
If your blood is drawn in the morning, fasting for 8–12 hours is usually recommended. However, if your test is scheduled later in the day, you can eat and drink normally. Always follow your provider’s specific instructions for your test.
  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