Serum Immunoglobulin G (IgG) concentration
This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps protect your body from infections by fighting bacteria and viruses.
["IgG levels help assess immune function and identify potential immune deficiencies or infections."]
Key facts at a glance
- LOINC
- 51536-1
- Short code
- Egg White IgG Ql
- Synonyms
- Egg White IgG Ql
- Category
- chemistry
- 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 IgG Measure?
IgG is the most abundant antibody in your blood and plays a critical role in long-term immunity. It’s produced by your immune system to defend against a wide range of pathogens, including bacteria and viruses. Measuring IgG helps doctors evaluate how well your immune system is working, especially in people with weakened immunity due to conditions like HIV, cancer treatments, or certain genetic disorders.
Why Might You Need This Test?
Your doctor may order an IgG test if you have symptoms like frequent infections, slow wound healing, or if you’re receiving treatments that suppress your immune system. It can also be used to monitor immune responses in people with autoimmune diseases or those receiving immune-boosting therapies.
Common Reasons for Testing
IgG testing is often done to diagnose or monitor conditions such as immunodeficiency diseases, infections (like tuberculosis or HIV), or to check immune responses before or after vaccination. It may also be part of a broader evaluation for chronic diseases like lupus or rheumatoid arthritis.
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, which usually takes a few minutes. If you’re on blood thinners or have a history of bleeding, let your doctor know beforehand.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
How IgG Levels Can Affect Your Health
Short name
IgG Level
Frequently asked questions
How long does it take to get IgG test results?
What do low IgG levels mean?
Can IgG 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