Immunoglobulin G (IgG) in Serum or Plasma (Mass Concentration)
This test measures the amount of Immunoglobulin G (IgG), a type of antibody found in your blood. IgG helps protect your body from infections by fighting bacteria and viruses.
["IgG antibodies are crucial for long-term immunity and are often checked if you have recurring infections or immune-related conditions."]
Key facts at a glance
- LOINC
- 27387-0
- Short code
- Deprecated S pneum14 IgG Ser-mCnc
- Synonyms
- Deprecated S pneum14 IgG Ser-mCnc
- 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 This Test Measure?
IgG is the most abundant antibody in your blood, playing a key role in defending against pathogens. This test quantifies its concentration to assess immune function and identify potential deficiencies or excesses.
Why Might You Need This Test?
Doctors may order an IgG test if you have symptoms like frequent infections, chronic illnesses, or if you’re being evaluated for immune disorders such as HIV, autoimmune diseases, or congenital immunodeficiency.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your blood is collected in the morning. Wear a loose shirt for easy access to your arm.
What Happens During the Test?
A healthcare provider will insert a small needle into a vein in your arm to collect a blood sample. You may feel a brief pinch, but it usually doesn’t cause significant discomfort. The process takes about 5 minutes.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low IgG levels may indicate an immune deficiency, while high levels could suggest chronic infections, certain cancers, or immune system overactivity. This test helps diagnose conditions like common variable immunodeficiency (CVID) or monitor treatment responses in patients with immune disorders.
Short name
IgG Level
Frequently asked questions
How long does it take to get results?
What does a low IgG level mean?
Can 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