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Serum Immunoglobulin G (IgG) Level

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 by binding to pathogens."]

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

Key facts at a glance

LOINC
24916-9
Short code
XR Sinuses Views
Synonyms
XR Sinuses Views
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
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 most common type of antibody in your blood. It plays a key role in defending your body against bacteria and viruses. Unlike other antibodies, IgG can cross the placenta to provide temporary immunity to a newborn. Levels of IgG can vary depending on your health, immune response, and past infections.

Why Might Your Doctor Order This Test?

Your doctor may request an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate immune responses to vaccines or treatments, or monitor chronic diseases that affect antibody production.

Common Uses of IgG Testing

IgG testing is often used in cases of recurrent infections, suspected immune deficiencies, autoimmune diseases, or to assess immune recovery after illness or treatment (e.g., chemotherapy). It can also help monitor immune responses in patients with conditions like HIV or after organ transplants.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, and you can eat and drink normally afterward. If you’re on blood thinners, let your doctor know before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How is IgG tested?
IgG is measured using a blood sample drawn from a vein in your arm. The test involves sending your blood to a lab, where it is analyzed using an immunoassay method to detect and quantify IgG antibodies.
What do my IgG results mean?
Your results will be compared to reference ranges for your age and health status. If your IgG level is outside the normal range, your doctor will discuss potential causes, such as infections, immune disorders, or medications that may affect antibody production. Follow-up tests or additional questions may be needed to understand the full picture.
Can IgG levels change over time?
Yes, IgG levels can fluctuate due to infections, vaccinations, chronic illnesses, or treatments like chemotherapy. Regular monitoring may be recommended if you have a condition affecting your immune system, such as HIV, autoimmune diseases, or certain cancers. Your doctor will guide you on how often to check your 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