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

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

This test measures the different types of Immunoglobulin G (IgG), a key antibody protein in your blood that helps fight infections and diseases.

Quick summary

["Understanding your IgG subclass levels can help identify immune system function and potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
107914-4
Short code
HLA I & II IgG SerPl
Synonyms
HLA I & II IgG SerPl
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 IgG Subclasses Are Measured?

IgG antibodies are divided into four subclasses (IgG1, IgG2, IgG3, and IgG4), each with distinct roles in immunity. This test evaluates the concentration of each subclass in your serum or plasma.

Why Might This Test Be Ordered?

Your healthcare provider may order this test to assess immune function, diagnose conditions like hypogammaglobulinemia (low IgG levels), evaluate immune responses to vaccines, or investigate autoimmune diseases.

What Does It Feel Like to Get the Test?

You’ll typically have a small needle inserted into your arm or vein to draw blood. The process is quick and usually painless, though some may feel slight discomfort.

What to Expect After the Test

After the blood draw, you can usually return to your normal activities immediately. If you experience bruising or soreness, apply a cold compress or take over-the-counter pain relievers as needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal IgG subclass levels can indicate immune system disorders, such as low resistance to infections (hypogammaglobulinemia), autoimmune conditions, or certain genetic disorders. High levels in specific subclasses may also be relevant in research or rare conditions.

Short name

IgG subclass levels

Frequently asked questions

When will I get my results?
Results are typically available within 2–5 business days, depending on your lab’s processing time. Your healthcare provider will discuss them with you during your follow-up visit.
What do my IgG subclass results mean?
Your results will show the concentration of each IgG subclass compared to a reference range. If your levels are outside the expected range, further testing or evaluation by your doctor may be needed to understand the cause.
Can I fast before this test?
No fasting is required for this test. Blood is drawn from a vein, and eating or drinking before the procedure does not affect the results.
  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