Serum Immunoglobulin G (IgG) Level
This test measures the amount of Immunoglobulin G (IgG), the most common type of antibody in your blood. IgG helps fight infections and is important for long-term immunity.
["IgG helps protect your body against infections and long-term immune responses."]
Key facts at a glance
- LOINC
- 94428-0
- Short code
- HLA class I + II IgG Pnl SerPl FC
- Synonyms
- HLA class I + II IgG Pnl SerPl FC
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- flow-cytometry
- 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 IgG Measure?
IgG is the primary antibody your immune system produces in response to infections, vaccines, and chronic illnesses. It circulates in your bloodstream and provides long-lasting protection by neutralizing toxins and pathogens. Low levels may indicate immune deficiencies or chronic illnesses, while high levels could suggest chronic infections, autoimmune conditions, or overactive immune responses.
Why Might You Need This Test?
Your doctor may order an IgG test to evaluate your immune system’s function, diagnose conditions like immunodeficiency, assess response to vaccines, or monitor chronic diseases such as lupus or rheumatoid arthritis. It’s also used in newborns to check for congenital immune disorders.
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 clotting factors), which is then tested for IgG levels. This test requires no special preparation, but fasting is often recommended for some related tests.
Test Results and Interpretation
Results are compared to standard reference ranges for your age and health status. While exact values vary, very low IgG levels may signal weakened immunity, while very high levels may warrant further investigation into chronic infections or immune disorders.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low IgG levels can indicate primary immunodeficiency diseases (e.g., severe combined immunodeficiency), chronic liver disease, or malabsorption issues that reduce nutrient absorption. High IgG levels may suggest chronic infections (e.g., hepatitis, HIV), autoimmune diseases (e.g., systemic lupus erythematosus), or overproduction by plasma cells in conditions like multiple myeloma. Repeated testing may be needed to monitor trends in immune function or disease progression.
Short name
IgG Level
Frequently asked questions
How Long Does It Take to Get Results?
Can I Eat or Drink Before the Test?
What If My IgG Level Is Outside the Normal Range?
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