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Immunoassay for Immunoglobulin G (IgG) in Serum or Plasma

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

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

Quick summary

["IgG levels help assess immune function and identify deficiencies or excesses."]

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

Key facts at a glance

LOINC
17019-1
Short code
IGF-I 2h p chal SerPl-mCnc
Synonyms
IGF-I 2h p chal SerPl-mCnc
Category
hormone
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 common type of antibody in your blood. It plays a key role in fighting off infections, including bacteria and viruses. Your body produces IgG in response to pathogens, helping to neutralize them and mark them for destruction by other immune cells. IgG also provides long-term immunity after an infection has passed.

Why Might You Need This Test?

Doctors may order an IgG test to evaluate your immune system, diagnose conditions like immunodeficiency, or check for immune-related disorders. It can also be used to monitor treatment responses in patients with chronic illnesses or autoimmune conditions.

Common Reasons for Testing

Common reasons include diagnosing immune deficiencies (e.g., common variable immunodeficiency), assessing immune responses to vaccines, evaluating symptoms like frequent infections, or monitoring conditions like lupus or other autoimmune diseases.

How Is the Test Done?

A blood sample is taken from a vein in your arm. The blood is then processed to separate the serum or plasma, which is sent to a lab for analysis using an immunoassay method to measure IgG levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance of IgG Levels

Short name

IgG Level

Frequently asked questions

What does an abnormal IgG level mean?
Low IgG levels may indicate an immune deficiency, where your body struggles to fight infections effectively. High IgG levels can sometimes suggest chronic infections, autoimmune diseases, or other conditions like multiple myeloma.
How often should I get this test?
The frequency depends on your medical condition and why the test was ordered. Your healthcare provider will determine the best schedule based on your needs, such as monitoring treatment progress or managing chronic illness.
Can diet or lifestyle affect IgG levels?
While diet and lifestyle factors like stress or sleep can influence immune function indirectly, they do not directly alter IgG levels. Focus on maintaining a balanced diet rich in nutrients to support overall immune health.
  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