IgG Immunoglobulin (Serum) – Total
This test measures the total amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG is the most common antibody and plays a key role in fighting infections and long-term immunity.
["IgG helps your body defend against bacteria and viruses and is crucial for long-term immunity."]
Key facts at a glance
- LOINC
- 22762-9
- Short code
- Deprecated S pneum12 IgG Ser-aCnc
- Synonyms
- Deprecated S pneum12 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 This Test Measure?
IgG is the primary antibody produced by your immune system to protect against infections. It circulates in your bloodstream and provides long-lasting immunity. This test quantifies the total concentration of IgG in your serum, which can help assess immune function, diagnose deficiencies, or monitor immune responses.
Why Might You Need This Test?
Doctors may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, recurrent illnesses, or unexplained fatigue. It may also be used to diagnose conditions like immunodeficiency disorders, monitor treatment for autoimmune diseases, or evaluate newborns for congenital immune deficiencies.
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 draw if your doctor specifies it, but this is not always required. Wear a comfortable shirt with an easy neckline for the phlebotomist to access your vein.
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 or sting, but it usually doesn’t cause significant discomfort. The blood is then sent to a lab for analysis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
IgG Level
Frequently asked questions
IgG levels can indicate immune system health. Low IgG may suggest an immunodeficiency, while high levels could be seen in chronic infections, autoimmune diseases, or certain medications. Monitoring IgG is particularly important in newborns, patients on long-term steroids, or those with chronic illnesses like HIV or cancer.
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss the results with you during your follow-up visit.
Low IgG levels can result from conditions like common variable immunodeficiency (CVID), HIV/AIDS, certain cancers, or long-term use of immunosuppressive medications. It may also occur in newborns if their mother had low IgG during pregnancy.
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