Immunoassay for Immunoglobulin G (IgG) in Serum/Plasma
This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps protect your body from infections and is the most common antibody in the blood.
["IgG helps fight infections and supports long-term immunity."]
Key facts at a glance
- LOINC
- 12909-8
- Short code
- IGF-I 30M p chal SerPl-mCnc
- Synonyms
- IGF-I 30M p chal SerPl-mCnc
- Category
- hormone
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- 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 against pathogens like bacteria and viruses. Levels of IgG can vary depending on your health status, immune response, and exposure to infections or vaccines.
Why Is IgG Tested?
Doctors may order an IgG test to diagnose or monitor conditions such as immune deficiencies, autoimmune diseases, infections, or to assess immune responses after vaccination. It can also help evaluate how well your immune system is functioning in people with chronic illnesses like HIV or cancer.
When Might You Need This Test?
You might need an IgG test if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It may also be part of a routine check-up for people with certain genetic or chronic conditions that affect immunity.
What to Expect Before the Test
No special preparation is usually needed for this blood test. You may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic or immune panel. On the day of the test, wear comfortable clothing and avoid eating or drinking anything (except water) if fasting is required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
IgG levels can indicate immune system health, help diagnose conditions like immunodeficiency, or assess immune responses to infections or vaccines. Low IgG levels may suggest an underlying immune disorder, while very high levels could be linked to chronic infections, autoimmune diseases, or certain medications.
Short name
IgG Level
Frequently asked questions
What causes IgG levels to be low?
What causes IgG levels to be high?
Does diet 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