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Serum Immunoglobulin G (IgG) by Immunoassay

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 fight infections and is the most common antibody in the body.

Quick summary

["IgG helps your immune system defend against bacteria and viruses."]

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

Key facts at a glance

LOINC
49095-3
Short code
SLEV IgG+IgM Ser-Imp
Synonyms
SLEV IgG+IgM Ser-Imp
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 the primary antibody produced by your immune system in response to infections, vaccines, and chronic diseases. It circulates in your bloodstream and provides long-term protection against pathogens. Low levels may indicate immune deficiencies, while high levels could suggest chronic infections, autoimmune conditions, or overproduction of antibodies.

Why Might You Need This Test?

Your healthcare provider may order this test to evaluate your immune system function, diagnose conditions like immunodeficiency, assess response to treatments for autoimmune diseases, or check for infections (e.g., HIV, hepatitis). It’s also used in newborns to monitor maternal antibody transfer.

Common Reasons for Testing

Common reasons include diagnosing or monitoring immune disorders, evaluating immune response to vaccines, checking for chronic infections, or assessing symptoms like frequent infections, fatigue, or unexplained illnesses.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. It usually takes a few minutes, and you may feel a brief pinch or discomfort.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

IgG Level

Frequently asked questions

Could my IgG levels be too low or too high?
Low IgG levels may suggest an immune deficiency, such as common variable immunodeficiency (CVID), where your body struggles to produce enough antibodies. High IgG levels could indicate chronic infections, autoimmune diseases (like rheumatoid arthritis), or conditions like multiple myeloma, where abnormal antibody production occurs.
Will my IgG test results affect my treatment?
Yes, your results may guide treatment decisions. For example, if your IgG is low, your doctor might recommend immune-boosting therapies, vaccines, or monitoring for infections. If high, further evaluation may be needed to rule out underlying causes like autoimmune diseases or cancer.
How often should I get this test?
Frequency depends on your health condition. If you have an immune disorder, your doctor may recommend regular testing. Otherwise, this test is often done as needed for diagnosis or monitoring specific symptoms or treatments.
  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