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Immunoglobulin G (IgG) in Serum

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 and diseases.

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
9460-7
Short code
Deprecated S pneum6+26 IgG Ser IA-aCnc
Synonyms
Deprecated S pneum6+26 IgG Ser IA-aCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 IgG Measure?

IgG is the most abundant antibody in your blood and is crucial for defending against bacteria and viruses. It provides long-term immunity by staying in your bloodstream longer than other antibodies.

Why Might You Need This Test?

Doctors may order an IgG test to check for low or high levels, which can happen due to immune system issues, infections, or certain medical conditions like HIV, autoimmune diseases, or malnutrition.

When Is an IgG Test Performed?

This test is often done when you have symptoms of a weakened immune system, such as frequent infections, unexplained weight loss, or if you’re being treated for conditions that affect antibodies.

What to Expect Before the Test

No special preparation is needed. A blood sample is taken from a vein in your arm, usually during a routine visit to your healthcare provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG Levels Can Indicate Immune Status

Short name

IgG Level

Frequently asked questions

Why was my IgG test ordered?
Your doctor may have ordered this test to evaluate your immune system function, diagnose conditions like immunodeficiency, or monitor treatment for diseases that affect antibody production.
What do my IgG results mean?
Results may be outside the normal range if you have an immune disorder, chronic infections, or other health conditions. Your doctor will discuss these findings with you in detail.
Can IgG levels change over time?
Yes, IgG levels can fluctuate due to infections, vaccinations, medications, or underlying health conditions. Regular monitoring may be needed if you have a chronic illness or immune-related disorder.
  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