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Serum or plasma mass concentration of immunoglobulin G (IgG) subclasses (specifically IgG1, IgG2, IgG3, IgG4) via immunoassay

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

This test measures the amount of specific types of antibodies (IgG subclasses) in your blood, which can help identify immune system function or deficiencies.

Quick summary

["IgG subclass tests help diagnose immune disorders or monitor immune responses."]

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

Key facts at a glance

LOINC
73746-0
Short code
KLH IgG Ser-mCnc
Synonyms
KLH IgG Ser-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
1.5
Ref high
9
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
83002
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 an immune system issue, such as frequent infections, unusual fatigue, or autoimmune conditions. It could also be used to check for immune-related problems in newborns or during pregnancy.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast before the test, but this depends on the lab’s instructions. Bring any medications you’re taking to your appointment.

How the Test Works

A blood sample is taken from a vein in your arm. The blood is then analyzed to measure the levels of IgG1, IgG2, IgG3, and IgG4 antibodies. The results help determine if any subclass is too high or too low.

Possible Results and Their Meaning

Results may show if one or more IgG subclasses are elevated or decreased compared to what’s expected. Low levels of certain subclasses might indicate immune deficiencies, while high levels could suggest chronic infections or other conditions.

Reference range

Follicular: 1.5-9.0 mIU/mLN/A

Specimen: serum

For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG subclass levels

Frequently asked questions

What Does This Test Detect?
This test helps identify immune system disorders, such as selective IgA deficiency, common variable immunodeficiency, or other conditions affecting antibody production. It can also be used to monitor treatment responses in patients with immune-related diseases.
What Are Normal Levels?
Normal ranges vary by lab and IgG subclass. Your results will be compared to your baseline or reference values provided by your healthcare provider.
How Often Should I Get This Test?
Your provider will determine how often you need retesting based on your symptoms, medical history, and treatment plan. Follow their instructions closely.
  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