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Immunoglobulin G (IgG) Subclass 1, Serum Concentration

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

This test measures the amount of Immunoglobulin G (IgG) subclass 1 in your blood. IgG is a key part of your immune system and helps fight infections.

Quick summary

["IgG1 helps protect against bacteria and viruses, and low levels may indicate immune system issues."]

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

Key facts at a glance

LOINC
12910-6
Short code
IGF-I 1h p chal SerPl-mCnc
Synonyms
IGF-I 1h p chal SerPl-mCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is IgG1 Used For?

IgG1 is one of four subclasses of Immunoglobulin G (IgG), a type of antibody in your blood. It plays a critical role in defending against infections by binding to pathogens and marking them for destruction by immune cells. Measuring IgG1 can help diagnose or monitor conditions affecting immune function, such as certain autoimmune diseases or immune deficiencies.

Why Might You Need This Test?

Your doctor may order an IgG1 test if you have symptoms like frequent infections, unusual fatigue, or if you’re being evaluated for conditions like HIV, lupus, or other immune-related disorders. It can also be part of routine monitoring for people with known immune system conditions.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it is analyzed using an immunoassay method to measure IgG1 levels. You may feel a slight pinch when the needle is inserted, but the process is quick and usually painless.

What Do Results Mean?

Results are compared to standard reference ranges for healthy adults. Very low IgG1 levels may suggest immune system problems, while very high levels could indicate chronic infections, certain cancers, or other conditions. Your doctor will interpret results in the context of your overall health and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG1 Levels and Health

Short name

IgG1 Level

Frequently asked questions

What could cause my IgG1 levels to be low?
Low IgG1 levels can occur due to immune deficiencies, such as selective IgA deficiency or common variable immunodeficiency. Chronic illnesses like HIV/AIDS, certain cancers (e.g., lymphoma), or long-term use of immunosuppressive medications may also lead to reduced IgG1. Rarely, genetic factors or severe malnutrition can contribute.
What might high IgG1 levels indicate?
Elevated IgG1 levels can be seen in chronic infections (e.g., tuberculosis, hepatitis), autoimmune diseases (e.g., rheumatoid arthritis), or certain types of cancer (e.g., multiple myeloma). In some cases, high IgG1 may reflect an overactive immune response or prolonged exposure to antigens.
How often should I get this test?
The frequency of IgG1 testing depends on your medical condition. If you have an immune-related disorder, your doctor may recommend regular monitoring. For routine health checks or if you’re asymptomatic, this test is usually not part of standard screening unless symptoms arise.
  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