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Immunoglobulin G (IgG) Subclass 1 and 3 Quantification (Serum/Plasma)

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

This test measures the levels of specific types of Immunoglobulin G (IgG), a key part of your immune system. IgG helps fight infections and provides long-term immunity.

Quick summary

["IgG subclasses play a role in immune defense and can be checked if you have symptoms of immune disorders or recurrent infections."]

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

Key facts at a glance

LOINC
99072-1
Short code
KLHL11 IgG Ser Ql CBA IFA
Synonyms
KLHL11 IgG Ser Ql CBA IFA
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
Method
cba-ifa
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 Is Done

Your healthcare provider may order this test if you have symptoms like frequent infections, autoimmune conditions, or if you’re being evaluated for conditions affecting your immune system. It can also be part of routine monitoring for certain diseases.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re on blood thinners, let your provider know before the test.

What the Results Mean

IgG subclasses are measured in arbitrary units per milliliter (U/mL) or milligrams per deciliter (mg/dL). Abnormal levels may indicate immune system issues, such as low or excessive antibody production.

Common Conditions Linked to IgG Subclass Levels

Low IgG levels may suggest immunodeficiency, while high levels could be linked to chronic infections, certain autoimmune diseases, or overproduction of antibodies. Your provider will interpret results in the context of your health history.

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.

IgG subclasses are part of the body’s immune response. IgG1 and IgG3 are particularly important for fighting bacterial and viral infections. Abnormal findings often prompt further evaluation for conditions like common variable immunodeficiency or other immune disorders.

Short name

IgG Subclass Levels

Frequently asked questions

What does a low IgG level mean?
A low IgG level may indicate a weakened immune system, which could increase your risk of infections. Your provider may recommend additional tests or treatments to support your immune function.
What does a high IgG level mean?
High IgG levels can sometimes signal chronic infections, autoimmune diseases, or overactive immune responses. Your provider will review your symptoms and other test results to understand the cause.
Can diet or lifestyle affect IgG subclass levels?
While diet and lifestyle factors may influence overall immune health, IgG subclass levels are primarily measured in a lab setting and are not directly affected by diet unless you have a known condition like celiac disease or malnutrition that impacts antibody production.
  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