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Serum IgG Substance Concentration (Mass Concentration)

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

This test measures the amount of Immunoglobulin G (IgG), a key antibody protein in your blood, which helps fight infections and supports immune function.

Quick summary

["IgG levels help assess your immune system’s strength and detect potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
40967-2
Short code
Deprecated S pneum34 IgG Ser-mCnc
Synonyms
Deprecated S pneum34 IgG Ser-mCnc
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 Is Immunoglobulin G (IgG)?

IgG is the most abundant antibody in your blood, produced by your immune system to defend against bacteria and viruses. It plays a vital role in long-term immunity by helping your body remember past infections and respond more quickly if exposed again.

Why Might You Need This Test?

Doctors may order an IgG test to evaluate immune function, diagnose conditions like immunodeficiency, monitor treatment responses, or investigate symptoms such as frequent infections, fatigue, or unexplained illnesses.

Common Reasons for Testing

Common reasons include diagnosing primary immune deficiencies (e.g., common variable immunodeficiency), assessing immune response to vaccines, evaluating chronic infections, or checking for autoimmune disorders that may affect antibody production.

What Does a Low or High IgG Level Mean?

Low IgG levels may indicate an immune system that struggles to fight infections, while high levels could suggest chronic inflammation, certain autoimmune diseases, or overproduction of antibodies.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How Is This Test Done?
A blood sample is drawn from your arm, and the serum (liquid part of blood without clots) is tested in a lab using an immunoassay method to measure IgG concentration.
What Does It Feel Like to Get a Blood Test?
You may feel a slight pinch or discomfort when the needle is inserted, but most people describe it as brief and manageable. Some people experience mild bruising or soreness afterward.
How Long Does It Take to Get Results?
Results are typically available within 1–3 business days, depending on lab processing times and your healthcare provider’s workflow.
  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