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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 plays a key role in long-term immunity.

Quick summary

["IgG helps fight infections and supports long-term immunity by identifying and neutralizing pathogens."]

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

Key facts at a glance

LOINC
27390-4
Short code
Deprecated S pneum19 IgG Ser-mCnc
Synonyms
Deprecated S pneum19 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 Does This Test Measure?

IgG is the most abundant antibody in your blood. It’s produced by your immune system to help defend against bacteria and viruses. Levels can vary based on your immune response, overall health, and exposure to infections or vaccines.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate immune responses to vaccines, or monitor chronic illnesses such as lupus or rheumatoid arthritis.

When Might You Get This Test?

You might receive this test if you have symptoms of a weakened immune system (e.g., frequent infections), if you’ve had a recent vaccination, or if your doctor suspects an underlying immune disorder.

What to Expect Before the Test

No special preparation is usually needed. You may be asked to fast before the test if it involves a blood draw, but this is not always required for IgG testing. Bring any medications or questions to your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What are normal IgG levels?
There is no single range considered 'normal' for everyone, as levels can vary based on age, health, and other factors. Your doctor will compare your results to your specific baseline and overall health.
How long does it take to get results?
Results are typically available within a few days to a week, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
Can diet or lifestyle affect IgG levels?
While diet and lifestyle can influence overall immune health, IgG levels are primarily determined by your immune system’s response. Stress, poor sleep, and chronic illness may indirectly affect immune function, but they don’t directly alter IgG test results.
  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