Serum or plasma concentration of immunoglobulin G (IgG) by nephelometry
This test measures the amount of Immunoglobulin G (IgG), a key protein in your immune system, found in your blood.
["IgG helps protect your body from infections and diseases by fighting harmful bacteria and viruses."]
Key facts at a glance
- LOINC
- 85956-1
- Short code
- S pneum Da 1 IgG Ser-aCnc
- Synonyms
- S pneum Da 1 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 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 in response to infections and helps remember past illnesses to prevent future infections. Levels can vary based on your health, immune response, and certain medical conditions.
Why Might You Need This Test?
Doctors may order an IgG test to check for immune system issues, such as low immunity (hypogammaglobulinemia), infections, or to monitor conditions like HIV, lupus, or other autoimmune diseases. It can also help diagnose or manage certain genetic disorders or after treatments like chemotherapy.
What to Expect Before the Test
No special preparation is usually needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re having a urine or other fluid test, follow your doctor’s instructions for timing and fasting if required.
What to Expect During the Test
The blood draw is quick and typically painless. If you experience discomfort, your healthcare provider may use a numbing cream or a different vein. If you’re nervous, remind them you’re okay to stop if needed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
IgG Level
Frequently asked questions
Low IgG levels may indicate a weakened immune system, putting you at higher risk for infections. High levels could suggest certain immune disorders, chronic infections, or overactive immune responses. Your doctor will interpret results in the context of your overall health and symptoms.
How often should I get this test?
Can I eat or drink before 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