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Immunoglobulin G (IgG) Subclass 1, Serum Concentration (Qualitative)

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

This test measures the level of Immunoglobulin G (IgG) subclass 1, a type of antibody in your blood. It helps assess immune function and identify potential deficiencies or imbalances.

Quick summary

["IgG1 antibodies play a key role in defending against certain infections and diseases."]

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

Key facts at a glance

LOINC
101871-2
Short code
IgLON5 IgG Titr CSF CBA IFA
Synonyms
IgLON5 IgG Titr CSF CBA IFA
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
cba-ifa
CPT
82977
SNOMED
3110003
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What Is IgG1 Used For?

IgG1 antibodies are part of your immune system’s response to infections, vaccines, and chronic conditions. Low levels may suggest immune dysfunction, while high levels could indicate chronic inflammation or autoimmune responses. This test is often used to diagnose or monitor conditions like immunodeficiency, autoimmune diseases, or immune-related side effects from treatments.

How Is This Test Performed?

A blood sample is drawn from a vein in your arm. The serum (liquid part of blood without clotting factors) is then tested using an immunoassay method to detect IgG1 levels. Results are qualitative (qualitative results indicate presence or absence rather than exact amounts).

Preparation for the Test

No special preparation is needed for this test. You may eat and drink normally before your appointment, unless instructed otherwise by your healthcare provider.

What Are Possible Results?

Results are qualitative, meaning they indicate whether IgG1 is present or not. If your test shows abnormal levels, your doctor may recommend further testing or additional evaluation of your immune system.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: csf

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG1 Subclass Screening

Frequently asked questions

Why might my doctor order this test?
Your doctor may recommend this test if you have symptoms of immune dysfunction (e.g., frequent infections, fatigue, or unexplained illnesses), suspected immunodeficiency, or if you’re undergoing treatment that could affect antibody production.
What does a low IgG1 level mean?
A low IgG1 level may suggest an immune system that isn’t producing enough antibodies to fight infections. This could be due to genetic disorders, chronic illnesses, or treatments like chemotherapy. Your doctor will discuss further steps, such as additional blood tests or lifestyle adjustments.
Do IgG1 levels change with age?
Yes, IgG1 levels can vary with age. Infants and young children typically have lower IgG1 levels compared to adults, as their immune systems develop. In older adults, IgG1 levels may also decline, potentially increasing susceptibility to infections. Your doctor will consider your age and overall health when interpreting 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