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Immunoglobulin G (IgG) in Serum or Plasma by Mass Concentration

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

This test measures the amount of Immunoglobulin G (IgG), the most common type of antibody in your blood. IgG helps fight infections and is important for long-term immunity.

Quick summary

["IgG levels help assess immune function and identify deficiencies or excesses that may affect your health."]

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

Key facts at a glance

LOINC
99414-5
Short code
Gamma glob SerPl IFE-mCnc
Synonyms
Gamma glob SerPl IFE-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immunofixation
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 Immunoglobulin G (IgG)?

IgG is the primary antibody produced by your immune system to protect against bacteria and viruses. It circulates in your blood and provides long-term immunity. Low levels may indicate immune system weakness, while high levels can sometimes suggest chronic infections or certain immune disorders.

Why Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of a weakened immune system (like frequent infections), if you’re being treated for an autoimmune condition, or if you’re planning a pregnancy to check for immune-related risks.

Common Reasons for Testing

Common reasons include diagnosing immune deficiencies, monitoring immune responses to treatments, evaluating chronic infections, or assessing risks in high-risk groups (e.g., newborns, transplant patients).

What to Expect Before the Test

No special preparation is needed, but you may fast for 8–12 hours before blood collection if instructed. A small needle will draw blood from your arm, and you may feel a brief pinch. The test uses a simple blood sample from a vein.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance of IgG Levels

Short name

IgG Level

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab. Follow-up with your doctor if you have questions about the results.
What do abnormal IgG levels mean?
Low IgG levels may indicate a congenital or acquired immune deficiency, while very high levels could suggest chronic infections, autoimmune diseases, or certain cancers. Your doctor will interpret results in the context of your health history.
Can IgG levels change with diet or medications?
IgG levels are primarily influenced by immune system activity and health conditions. While diet and some medications (like steroids) can indirectly affect immune function, they don’t directly alter IgG concentrations. Always discuss any concerns with your healthcare provider.
  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