Immunoglobulin G (IgG) Subclass 1 (Serum)
This test measures the level of Immunoglobulin G (IgG) subclass 1, a type of antibody in your blood. IgG is important for fighting infections and providing long-term immunity.
["IgG1 helps protect against bacteria and viruses, and its levels can indicate immune system health or response to treatments."]
Key facts at a glance
- LOINC
- 31648-9
- Short code
- Deprecated S pneum6 IgG Ser-aCnc
- Synonyms
- Deprecated S pneum6 IgG Ser-aCnc
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 Does This Test Measure?
IgG1 is one of four subclasses of Immunoglobulin G (IgG), the most common antibody in your blood. It plays a key role in defending against infections by neutralizing toxins and viruses. Measuring IgG1 helps assess immune function, especially in conditions like autoimmune diseases, infections, or immune deficiencies.
Why Might You Need This Test?
Your doctor may order this test if you have symptoms of an immune disorder, such as frequent infections, unusual fatigue, or autoimmune conditions. It can also be used to monitor treatment responses in certain diseases.
Sample Collection and Preparation
A blood sample is drawn from a vein in your arm. The blood is processed to separate serum (the liquid part without clots), which is then tested for IgG1 levels. This test is typically done in a lab using an immunoassay method to detect and measure the antibody.
What to Expect Before the Test
No special preparation is needed for this test. You may have some mild discomfort from the needle, but it usually goes away quickly. If you are on blood-thinning medication, let your doctor know before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low IgG1 levels may suggest immune system issues, such as primary immunodeficiency, chronic infections, or certain autoimmune diseases. High levels could be seen in conditions like multiple myeloma or certain inflammatory disorders. Monitoring IgG1 helps guide treatment decisions for immune-related conditions.
Short name
IgG1 Subclass (Serum)
Frequently asked questions
What Are Normal Results?
How Often Should I Get This Test?
Can Diet or Supplements Affect This 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