Immunoglobulin G (IgG) in serum/plasma
This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps protect your body from infections and is important for long-term immunity.
["IgG levels help assess immune function and detect deficiencies or excesses that may affect your health."]
Key facts at a glance
- LOINC
- 51531-2
- Short code
- BLGG
- Synonyms
- B-Lactoglob IgG Ql
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top vacutainer tube
- Units
- N/A
- Ref low
- 0
- Ref high
- 0.35
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Immunoassay (e.g., ELISA, FEIA, or immunocap) for detection of IgG antibodies specific to beta-lactoglobulin
- CPT
- 86001
- SNOMED
- 415684009
- Specimen volume
- 1.0 mL serum (minimum 0.5 mL)
- Stability
- Serum stable for 7 days at 2–8°C; for longer storage, freeze at -20°C or below for up to 4 weeks. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
What Is Immunoglobulin G (IgG)?
IgG is the most common type of antibody in your blood. It plays a key role in fighting off infections by helping your immune system remember past illnesses and respond more quickly if you encounter the same pathogen again. IgG is also involved in protecting tissues and organs from damage caused by infections.
Why Might You Need This Test?
Your doctor may order an IgG test to check for immune system problems, such as low levels (hypogammaglobulinemia) that could increase your risk of infections. It may also be used to monitor conditions like autoimmune diseases, certain cancers, or after treatments that weaken the immune system.
When Is an IgG Test Performed?
This test is often done as part of a routine blood check or when symptoms like frequent infections, fatigue, or unexplained illnesses are present. It may also be part of a workup for conditions like HIV, lupus, or after organ transplants to ensure proper immune function.
How Is the Test Done?
A small blood sample is taken from a vein in your arm. The blood is then sent to a lab for analysis to measure the amount of IgG antibodies present.
Reference range
Negative: <0.35 kU/L; Equivocal: 0.35–0.69 kU/L; Positive: ≥0.70 kU/L. Interpretive reporting: Detected (Positive) or Not detected (Negative).N/A
No fasting required. Patient should inform the ordering provider about current medications, especially antihistamines (which may affect related IgE allergy testing, but not IgG), and recent dietary exposure to cow's milk or dairy products. Avoid sample collection during acute illness when possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
IgG Level
Frequently asked questions
What Are Normal IgG Levels?
How Long Does It Take to Get Results?
Can Diet or Lifestyle 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 15, 2026. · Read our editorial policy