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Serum or Plasma Immunoassay for Immunoglobulin G (IgG) Substance Concentration

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 is important for long-term immunity.

Quick summary

["IgG helps fight infections and supports long-term immunity by marking viruses and bacteria for destruction."]

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

Key facts at a glance

LOINC
106053-2
Short code
Rf Igm & Iga pnl SerPl
Synonyms
Rf Igm & Iga pnl SerPl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
86430
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 IgG and Why Is It Measured?

IgG is the most common type of antibody in your blood. It plays a key role in defending against bacterial and viral infections. Your body produces IgG in response to infections or vaccines, helping you build immunity over time. This test helps doctors assess your immune system’s ability to fight certain pathogens.

When Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, slow healing wounds, or unexplained fatigue. It may also be used to monitor immune responses after vaccines, diagnose conditions like immunodeficiency, or evaluate immune-related diseases.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then processed to separate serum or plasma, which is tested for IgG levels using an immunoassay method. This method detects the presence and concentration of IgG antibodies in your blood.

What Do Results Mean?

Results are compared to standard reference ranges, but exact values can vary by lab. Low IgG levels may indicate an immune deficiency, while very high levels might suggest overactive immune responses or certain medical conditions. Your doctor will interpret results in the context of your health history and symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Why might my IgG levels be checked if I have frequent infections?
Low IgG levels can signal an immune system that isn’t producing enough antibodies to fight infections effectively. This could be due to a congenital immunodeficiency, autoimmune diseases, or conditions like HIV/AIDS that weaken immunity. Your doctor may recommend further testing or treatments to address the underlying cause.
Could high IgG levels be a cause for concern?
Very high IgG levels can sometimes indicate chronic infections, certain cancers (like multiple myeloma), or autoimmune diseases where the immune system produces excessive antibodies. While less common, these findings should be evaluated by your healthcare provider to determine the best next steps.
How often should I expect to have this test?
The frequency depends on your medical condition and treatment plan. If you have a chronic illness or are undergoing immune-related therapy, your doctor may order this test regularly. Otherwise, it’s usually done only when symptoms or concerns arise.
  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