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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 is important for long-term immunity.

Quick summary

["IgG helps fight infections and supports long-term immunity."]

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

Key facts at a glance

LOINC
42206-3
Short code
IgA CSF/SerPl
Synonyms
IgA CSF/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
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 This Test Measure?

IgG is one of the most common types of antibodies in your blood. It plays a key role in defending your body against bacteria, viruses, and toxins. Levels can vary depending on your immune response, overall health, and exposure to infections.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, monitor treatment for certain diseases, or evaluate immune responses after vaccination.

When Might You Get This Test?

You might have this test if you have symptoms of a weakened immune system (such as frequent infections), if you’re being treated for an autoimmune disease, or if you’re planning to receive a vaccine and your doctor wants to ensure your immune response will be strong.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into your arm or vein to draw blood. If a blood sample is taken from your finger, it may cause a small bruise or sting briefly.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

What Does a Low or High 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 an overactive immune response, chronic infections, or certain autoimmune conditions, but this isn’t always the case.
How Often Should I Get This Test?
The frequency depends on your health condition and treatment plan. Your doctor will determine how often you need retests, especially if you have a chronic illness or are receiving immune-modifying treatments.
Can Diet or Lifestyle Affect IgG Levels?
While diet and lifestyle factors like stress or sleep can influence overall health, they don’t directly affect IgG levels. However, maintaining a balanced diet and good health can support your immune system’s ability to function properly.
  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