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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 protein in your immune system that helps fight infections.

Quick summary

["IgG subclasses help identify immune responses and potential deficiencies in immune protection."]

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

Key facts at a glance

LOINC
47497-3
Short code
Deprecated S pneum43 IgG sp1 Ser-mCnc
Synonyms
Deprecated S pneum43 IgG sp1 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 order this test to evaluate immune function, diagnose conditions like chronic infections, autoimmune diseases, or immune system disorders, or to monitor treatment responses in patients with certain conditions such as HIV, lupus, or other immune-related illnesses.

What to Expect Before the Test

No special preparation is typically needed. You may be asked to fast for 8–12 hours before the test if blood is drawn early in the morning, but this is not always required. Bring any medications or supplements you’re currently taking to your appointment.

What Happens During the Test

A healthcare professional will collect a blood sample from a vein in your arm using a small needle. The blood will be sent to a lab for analysis to measure IgG subclass concentrations in your serum.

What the Results Mean

Results show the concentration of IgG subclasses (IgG1, IgG2, IgG3, IgG4) in your blood. Abnormal levels may indicate immune system issues, such as low resistance to infections or overactive immune responses.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Subclass Levels

Frequently asked questions

What does a low or high IgG subclass level indicate?
Low levels of specific IgG subclasses may signal weakened immune responses, increasing susceptibility to infections. High levels could be linked to chronic immune activation, autoimmune diseases, or certain infections. Your doctor will discuss findings with you based on your medical history and symptoms.
How often should I get this test?
Frequency depends on your health condition and treatment plan. Some patients may need this test annually or more often if they have ongoing immune-related issues. Your healthcare provider will determine the best schedule for you.
Can lifestyle changes affect IgG subclass levels?
While diet, stress, and overall health can influence immune function, IgG subclass levels are primarily determined by your body’s immune response. However, maintaining a balanced diet rich in vitamins (like vitamin D and B12) and staying hydrated may support overall immune health.
  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