Immunoglobulin G (IgG) in Serum
This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood serum. IgG helps protect your body from infections and is the most common antibody found in the blood.
["IgG antibodies play a key role in long-term immunity and are often checked if you have recurring infections or immune-related conditions."]
Key facts at a glance
- LOINC
- 47326-4
- Short code
- Deprecated S pneum17 IgG 2:1 Ser-Rto
- Synonyms
- Deprecated S pneum17 IgG 2:1 Ser-Rto
- 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 your immune system produces in response to infections, vaccines, and some diseases. It circulates in your bloodstream and helps neutralize harmful substances like bacteria and viruses. This test helps doctors assess your immune response and identify potential deficiencies or overproduction of IgG.
Why Might You Need This Test?
Your doctor may order an IgG test if you have symptoms like frequent infections, low energy, or if you’re being treated for conditions like HIV, autoimmune diseases, or certain cancers. It can also be part of routine monitoring for people with immune system disorders.
Preparation for 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. If you’re on blood thinners or have a history of bleeding issues, let your doctor know before the test.
What to Expect After the Test
After the blood is drawn, you may feel a slight pinch or discomfort for a few seconds. The site will be covered with a bandage. You can resume normal activities immediately. Rarely, you might experience bruising or swelling at the injection site.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low IgG levels may indicate an immune deficiency, such as common variable immunodeficiency (CVID), where your body struggles to fight infections. High IgG levels can sometimes be seen in chronic infections, autoimmune diseases, or after receiving repeated vaccines. Doctors use these results to guide treatment, such as immune therapy or adjusting medication.
Short name
IgG Level
Frequently asked questions
What does an abnormal IgG level mean?
Can IgG levels change over time?
Is there anything I should avoid 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