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Serum or plasma concentration of immunoglobulin G (IgG) by nephelometry

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 the most common type of antibody.

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
45355-5
Short code
Date Rh imm gl Gvn
Synonyms
Date Rh imm gl Gvn
Category
chemistry
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 primary antibody in your blood that fights off bacteria and viruses. It’s produced by your immune system to defend against infections and is found in all body fluids. Your body produces IgG throughout your life to remember past infections and provide long-term protection.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system issues, such as low IgG levels (hypogammaglobulinemia), which can make you more prone to infections. It’s also used in diagnosing conditions like HIV, certain autoimmune diseases, or after organ transplants to monitor immune response.

When Could You Expect Results?

Results are typically ready within a few days to a week, depending on your lab’s processing time. Your healthcare provider will discuss the results with you during your follow-up visit.

Common Reasons for Testing

Recurrent infections, unexplained fatigue, or symptoms like frequent colds or sinus infections may prompt this test. It’s also used in newborns to check for immune deficiencies or in patients receiving immune-suppressing treatments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How often should I get this test?
The frequency depends on your health condition. If you have a known immune disorder, your doctor may recommend regular monitoring. Otherwise, this test is usually done only when symptoms or concerns arise.
What does a low IgG level mean?
Low IgG levels can indicate a weakened immune system, making you more susceptible to infections. It may be linked to conditions like HIV, certain cancers, or genetic immune disorders. Your doctor will evaluate other symptoms and test results to determine the cause.
Can diet or supplements affect IgG levels?
Dietary changes alone won’t significantly alter IgG levels, but a balanced diet rich in protein and vitamins supports overall immune function. Supplements like vitamin D or zinc may indirectly support immune health, but they won’t directly measure IgG levels.
  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