Serum Immunoglobulin G (IgG) by Immunoassay
This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps fight infections and is the most common antibody in the body.
["IgG helps protect your immune system and is often checked if you have symptoms of infection or immune-related conditions."]
Key facts at a glance
- LOINC
- 9338-5
- Short code
- RF IgM Ser IA-aCnc
- Synonyms
- RF IgM Ser IA-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- CPT
- 86430
- 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
Why This Test Might Be Ordered
Your healthcare provider may order this test to check for low or high levels of IgG, which can happen due to immune system issues, infections, or certain medical conditions like HIV, lupus, or autoimmune diseases. It’s also used to monitor treatment for conditions like leukemia or to assess immune function in newborns or people with weakened immune systems.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. If you’re on blood thinners or have a history of bleeding, let your provider know before the test.
What the Results Mean
IgG levels can vary based on age, overall health, and medical conditions. Low IgG might indicate a weakened immune system, while very high levels could suggest overactive immune responses or certain diseases. Your provider will discuss your results in the context of your health history.
Common Conditions Monitored
IgG levels are often checked in people with chronic illnesses like HIV/AIDS, autoimmune diseases (e.g., rheumatoid arthritis), or those who’ve had organ transplants. It’s also used in newborns to check for immune deficiencies.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG is crucial for long-term immunity. Low levels can leave you vulnerable to infections, while high levels may signal inflammation, infections, or certain cancers. Your provider will interpret results alongside other symptoms and tests to determine the best next steps.
Short name
IgG Level
Frequently asked questions
What causes IgG levels to change?
How long does it take to get results?
Can diet or supplements affect IgG levels?
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