IgG Immunoglobulin Subclass 1 (Serum)
This test measures the level of Immunoglobulin G (IgG) subclass 1, a type of antibody in your blood. IgG1 is one of the main components of the immune system that helps fight infections and diseases.
["IgG1 helps protect your body by identifying and neutralizing harmful substances."]
Key facts at a glance
- LOINC
- 102848-9
- Short code
- Yogurt IgE RAST
- Synonyms
- Yogurt IgE RAST
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- rast
- CPT
- 84484
- SNOMED
- 302774002
- 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. This test specifically looks at the concentration of IgG1, which plays a key role in immune defense. Levels can vary depending on your immune response, health status, and certain medical conditions.
Why Might You Need This Test?
Your healthcare provider may order this test if you have symptoms or conditions that could involve immune system issues, such as recurrent infections, autoimmune diseases, or certain allergies. It may also be used to monitor treatment responses in conditions like chronic infections or immune-related disorders.
Common Reasons for Testing
Tests like this are often part of broader evaluations for immune function. They can help diagnose or monitor conditions where IgG1 levels might be abnormal, such as in immune deficiencies, certain cancers, or after receiving immune-modifying treatments.
What to Expect Before the Test
No special preparation is usually needed for this blood test. You may be asked to fast for a few hours before the draw, but this depends on your healthcare provider’s instructions. A healthcare professional will collect a small amount of blood from a vein in your arm.
Reference range
Adult: 10-40 U/LN/A
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
Frequently asked questions
What Are My IgG1 Levels Telling Me?
How Do My IgG1 Results Compare to Others?
Can IgG1 Levels Change Over Time?
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 17, 2026. · Read our editorial policy