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Immunoglobulin G (IgG) Subclass 3 Quantification (Serum)

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

This test measures the amount of Immunoglobulin G (IgG) subclass 3, a type of antibody in your blood. IgG3 is part of your immune system and helps fight infections.

Quick summary

["IgG3 helps protect against certain bacteria and viruses by marking them for destruction by immune cells."]

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

Key facts at a glance

LOINC
109380-6
Short code
GM3 IgG Msmt Ser
Synonyms
GM3 IgG Msmt 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

What Is IgG3 Used For?

IgG3 levels may be checked if you have conditions that affect your immune system, such as autoimmune diseases, infections, or certain immune deficiencies. It can also help monitor treatment responses in some cases.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms like frequent infections, unusual fatigue, or if you’re being treated for an immune-related condition. It may also be part of a broader immune evaluation.

How Is the Test Done?

A blood sample is drawn from a vein in your arm. The blood is then processed to separate serum, where the IgG3 level is measured using a specialized immunoassay technique.

What Do My Results Mean?

Results may indicate whether your IgG3 levels are within expected ranges or if they are lower or higher than normal. Abnormal levels could suggest immune system issues or other health concerns that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG3 Level

Frequently asked questions

Why do some people have lower than normal IgG3 levels?
Lower IgG3 levels can occur due to immune system disorders, such as hypogammaglobulinemia, certain autoimmune diseases, or after treatments that weaken the immune response. It may also be part of a broader immune evaluation if you have frequent infections or other symptoms.
What if my IgG3 level is higher than expected?
Elevated IgG3 levels can sometimes be seen in chronic infections, certain autoimmune conditions, or in response to long-term immune stimulation. Your healthcare provider will consider your overall health and symptoms to determine if this finding is significant.
Can IgG3 levels change over time?
Yes, IgG3 levels can fluctuate due to infections, immune responses, medications, or underlying health conditions. Regular monitoring may be needed if you have a condition affecting your immune system, such as HIV, lupus, or certain cancers.
  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