Immunoglobulin G (IgG) Subclass 1 (Serum) – Quantitative
This test measures the amount of Immunoglobulin G (IgG) subclass 1, a type of antibody in your blood. IgG1 is one of the main components of your immune system, helping fight infections and diseases.
["IgG1 helps protect your body by identifying and neutralizing harmful substances, like bacteria and viruses."]
Key facts at a glance
- LOINC
- 10401-8
- Short code
- ISG Gvn
- Synonyms
- ISG Gvn
- Category
- chemistry
- 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 Does This Test Measure?
IgG1 is a subtype of Immunoglobulin G (IgG), which is the most common antibody in your blood. It plays a critical role in long-term immunity by binding to pathogens (such as bacteria and viruses) and marking them for destruction by other immune cells. This test specifically looks at the concentration of IgG1, which can vary depending on your immune response, health status, and other factors.
Why Might You Need This Test?
Doctors may order an IgG1 test to evaluate immune function, diagnose or monitor conditions affecting antibody levels, or assess responses to treatments like vaccines or medications that boost immunity. It can also help identify immune deficiencies or autoimmune disorders.
Common Uses and Conditions
IgG1 testing is often used in cases of suspected immune system disorders, such as hypogammaglobulinemia (low IgG levels), certain autoimmune diseases, or after receiving immune-modifying treatments. It may also be part of a broader evaluation for recurrent infections or unexplained symptoms related to immunity.
What to Expect Before the Test
No special preparation is usually needed for this blood test. You may be asked to fast for 8–12 hours before the draw if your lab requires it, but this is not always the case. Bring your test list or any medications you’re currently taking to your appointment.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG1 levels can provide insight into your immune system’s ability to produce protective antibodies. Low IgG1 levels may indicate an immune deficiency, while elevated levels could suggest an overactive immune response, chronic infection, or certain autoimmune conditions. This test is often part of a larger diagnostic workup rather than a standalone evaluation.
Short name
IgG1 Subclass Level
Frequently asked questions
Will this test involve fasting?
How long will results take to get?
Can I eat or drink before the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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