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IgG (Immunoglobulin G), Serum

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

A blood test that measures the amount of IgG, the most abundant type of antibody, in serum.

Quick summary

["This test shows how much IgG is present in your blood and may help evaluate immune function or suspected immune disorders."]

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

Key facts at a glance

LOINC
109029-9
Short code
SAE1 IgG Msmt Ser
Synonyms
SAE1 IgG Msmt Ser
Category
kidney
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 is this test?

IgG is an antibody that helps the immune system recognize and fight infections. This test measures the concentration of IgG in serum, the liquid portion of a blood sample.

Why might I need this test?

A serum IgG test may be ordered to evaluate immune function, investigate recurrent infections, or assess conditions involving abnormal antibody production. It may also be used as part of an evaluation for a monoclonal protein or other immune-related condition.

How is the test performed?

Blood is collected from a vein and allowed to separate so the serum can be analyzed. The laboratory typically measures IgG with an immunoassay or another validated quantitative method.

How do I prepare for the test?

No special preparation is usually required for a routine serum IgG test. Follow your healthcare professional's instructions and tell the laboratory if you are taking immune-modulating medicines or recently received antibody treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

A low IgG level may be associated with impaired antibody production or immunodeficiency, although other factors can also affect the result. An elevated IgG level can occur with chronic infection, inflammatory conditions, liver disease, or a monoclonal immune-cell disorder. The result should be interpreted with symptoms, other laboratory tests, and the laboratory's reference interval.

Short name

Serum IgG

Frequently asked questions

What does IgG measure?
The test measures the concentration of immunoglobulin G, an antibody that is important for fighting infections.
Is a serum IgG test the same as an IgG antibody blood test?
No. A serum IgG test measures the total amount of IgG in the blood, while an IgG antibody test usually measures IgG directed against a specific substance, infection, or allergen.
Does an abnormal IgG result diagnose a specific condition?
No. An abnormal result is not diagnostic by itself and must be interpreted alongside your symptoms, medical history, and other laboratory findings.
  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