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Immunoglobulin G (IgG) Subclass 1 (Serum) – Quantitative

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

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood, specifically focusing on the IgG1 subclass. IgG is important for fighting infections and providing long-term immunity.

Quick summary

["IgG1 helps protect against bacterial and viral infections and plays a role in immune responses."]

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

Key facts at a glance

LOINC
96477-5
Short code
IgLON5 IgG Titr Ser IF
Synonyms
IgLON5 IgG Titr Ser IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82977
SNOMED
3110003
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 Does This Test Measure?

IgG1 is one of the four subclasses of Immunoglobulin G (IgG), a key antibody in your immune system. This test quantifies the concentration of IgG1 in your serum, helping doctors assess immune function, diagnose conditions like hypogammaglobulinemia, or evaluate immune responses to treatments or infections.

Why Might This Test Be Ordered?

Your healthcare provider may order this test if you have symptoms of a weakened immune system, such as frequent infections, recurrent colds, or unexplained illnesses. It may also be used to monitor immune-related conditions, check for immune deficiencies, or evaluate responses to therapies like chemotherapy or immune-modulating treatments.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The blood is processed to separate serum (the liquid part after clotting), which is then analyzed in a laboratory using immunoassay methods to measure IgG1 levels.

What Are Possible Results?

Results are typically reported as a concentration value (e.g., grams per liter) compared to a reference range. While reference ranges can vary slightly by lab, they generally reflect normal levels of IgG1 in healthy individuals. Abnormal results may indicate immune system issues or other health concerns.

Reference range

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

Specimen: serum

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 Level

Frequently asked questions

What does an abnormal IgG1 level mean?
Low IgG1 levels may suggest an immune deficiency, such as selective IgA deficiency or common variable immunodeficiency, which can increase susceptibility to infections. High IgG1 levels might be seen in chronic infections, autoimmune diseases, or certain inflammatory conditions. Always discuss results with your healthcare provider for personalized interpretation.
How often should I get this test?
The frequency of testing depends on your medical condition and treatment plan. If you have a known immune disorder, your doctor may recommend regular monitoring. If this test is part of a routine checkup or screening, follow their guidance on timing.
Can lifestyle or diet affect IgG1 levels?
While diet and lifestyle factors like stress or infections can influence immune function broadly, IgG1 levels are primarily influenced by immune system activity and health conditions. Your doctor may advise dietary or lifestyle adjustments if they suspect underlying factors affecting your immune response.
  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