Skip to content

Serum IgG Immunoglobulin Subclass 1 (IgG1) Level

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

This test measures the amount of Immunoglobulin G (IgG), a type of antibody, specifically the IgG1 subclass found in your blood serum. IgG antibodies help protect your body from infections and diseases.

Quick summary

["IgG1 helps fight infections and supports immune function; low levels may indicate immune system issues."]

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

Key facts at a glance

LOINC
40989-6
Short code
RSV IgG Ser Ql IA
Synonyms
RSV IgG Ser Ql IA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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

What Is IgG1 Used For?

IgG1 levels are often checked when evaluating immune responses, diagnosing autoimmune conditions, or assessing immune deficiencies. It may also be used in research or specialized clinical scenarios to monitor antibody production.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of weakened immunity, such as frequent infections, unexplained fatigue, or if you’re being treated for an autoimmune disease. It could also be part of a broader immune workup.

How Is the Test Performed?

A blood sample is drawn from a vein, typically in your arm. The serum portion is separated and analyzed using an immunoassay method to detect IgG1 levels.

What Do Results Mean?

Results may be compared to reference ranges for healthy individuals, but exact values can vary by lab. Low IgG1 levels might suggest immune dysfunction, while high levels could indicate chronic infections or certain immune disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG1 plays a critical role in long-term immunity by targeting bacteria and viruses. Reduced IgG1 levels may correlate with conditions like common variable immunodeficiency (CVID) or other immune deficiencies, while elevated levels could signal chronic inflammation or autoimmune responses.

Short name

IgG1 Subclass

Frequently asked questions

What causes IgG1 levels to change?
IgG1 levels can be influenced by infections, autoimmune diseases, immune system treatments (like steroids), or genetic factors. Chronic illnesses, aging, or certain medications may also affect antibody production.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Follow up with your healthcare provider for interpretation.
Can lifestyle changes affect IgG1 levels?
While diet and exercise generally support immune function, IgG1 levels are primarily influenced by immune system activity. Stress, poor sleep, or infections may temporarily impact antibody responses.
  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