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Serum Immunoglobulin G (IgG) Level

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of Immunoglobulin G (IgG), a type of antibody in your blood. IgG helps protect your body from infections.

Quick summary

["IgG antibodies play a key role in long-term immunity."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
86117-9
Short code
S pneum Da 4 IgG 2:1 Ser-Rto
Synonyms
S pneum Da 4 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 most abundant antibody in your blood, providing broad protection against various pathogens like bacteria and viruses. It’s produced by plasma cells in response to infections or vaccines. Levels can vary based on your immune response, overall health, and exposure to infections.

Why Might You Need This Test?

Doctors may order an IgG test to diagnose or monitor conditions like immunodeficiency, chronic infections, autoimmune diseases, or to check immune response after vaccination. It can also help evaluate long-term health in people with weakened immune systems.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure IgG concentration. No special preparation is needed, but fasting may be advised depending on the lab’s protocol.

What Are Common Uses?

IgG testing is commonly used in pediatric care to assess immune function in infants and children, in adults to diagnose conditions like HIV/AIDS, or to monitor treatment responses in chronic diseases.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical significance: Low IgG levels may indicate a primary immunodeficiency, chronic infections, or malabsorption issues. Elevated levels could suggest chronic inflammation, certain cancers, or autoimmune disorders. Always discuss results with your healthcare provider, as they’ll consider your full medical history and symptoms.

Short name

IgG Level

Frequently asked questions

What does a low IgG level mean?
A low IgG level may mean your immune system isn’t producing enough antibodies to fight infections effectively. This could be due to a genetic immunodeficiency, long-term illness, or conditions affecting nutrient absorption.
How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab and insurance. Follow-up with your doctor to discuss the meaning of your results.
Can diet affect IgG levels?
Diet can indirectly influence immune function, but IgG levels are primarily determined by your body’s immune response. Focus on a balanced diet to support overall health, but avoid assuming specific foods directly raise or lower IgG levels.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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