IgG Immunoglobulin Subclass 1 (Serum)
This test measures the amount of Immunoglobulin G (IgG), a type of antibody, specifically the IgG1 subclass found in your blood serum. IgG antibodies play a key role in defending against infections and are part of your immune response.
["IgG1 antibodies help fight bacteria and viruses, and their levels can indicate immune function or response to treatments."]
Key facts at a glance
- LOINC
- 13261-3
- Short code
- L mexicana IgM Ser-aCnc
- Synonyms
- L mexicana IgM Ser-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 86038
- 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), the most common antibody in your blood. This subclass is particularly important for providing long-term immunity against bacterial and viral infections. Your body produces IgG1 in response to vaccines, infections, and other immune challenges. Levels can vary based on your immune system’s activity, health status, or exposure to pathogens.
Why Might Your Doctor Order This Test?
Doctors may request IgG1 subclass testing to evaluate immune function, assess responses to treatments (like vaccines or medications), or investigate conditions affecting antibody production. For example, it could help diagnose or monitor autoimmune diseases, immunodeficiency disorders, or certain infections.
Common Uses and Conditions
IgG1 testing is often used in conjunction with other antibody tests to diagnose or monitor conditions such as HIV, hepatitis, certain autoimmune diseases (e.g., lupus), or immune deficiencies. It may also help evaluate vaccine effectiveness or guide treatment plans for patients with weakened immune systems.
What to Expect Before the Test
No special preparation is usually needed for this blood test. You may fast for 8–12 hours before the draw if instructed by your healthcare provider, but this is not always required. A small needle will be used to collect blood from a vein in your arm. The process is quick and typically painless.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG1 levels can provide insights into your immune system’s ability to produce antibodies. Low levels may suggest immunodeficiency, chronic infections, or certain autoimmune diseases. High levels could indicate an active immune response (e.g., infection, inflammation, or overproduction of antibodies). Your doctor will interpret results in the context of your overall health and medical history.
Short name
IgG1 Subclass
Frequently asked questions
How Does IgG1 Testing Differ from Other Antibody Tests?
What Are Typical Reference Ranges?
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 16, 2026. · Read our editorial policy