Skip to content

Immunoglobulin G (IgG) in Serum

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 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
47325-6
Short code
Deprecated S pneum17 IgG sp2 Ser IA-mCnc
Synonyms
Deprecated S pneum17 IgG sp2 Ser IA-mCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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 IgG Serially Measure Over Time?

IgG levels can be monitored over time to assess immune response, especially after vaccination, treatment for infections, or in conditions affecting the immune system. Repeated testing may help track changes in your immune status or response to therapy.

Why Might IgG Testing Be Done?

Your healthcare provider may order this test to evaluate immune function, diagnose or monitor conditions like immunodeficiency, check for immune response to vaccines, or investigate symptoms such as frequent infections.

How Is This Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate serum (the liquid part without clotting factors), which is analyzed for IgG levels using an immunoassay method.

What Are Common Reasons for Abnormal Results?

Low IgG levels may indicate a weakened immune system, while high levels could be due to chronic infections, certain immune disorders, or overproduction of antibodies. Results should always be interpreted by a healthcare provider in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Why do I need repeated IgG testing?
Repeated IgG testing may be needed to monitor your immune response to treatments, vaccines, or to track changes in your immune system over time, especially if you have conditions like immunodeficiency or chronic infections.
What does it mean if my IgG levels are lower than expected?
Lower IgG levels may signal a weakened immune system, which could make you more prone to infections. Your healthcare provider will discuss this with you and may recommend further evaluation or treatment to address the underlying cause.
How long does it take to get IgG test results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will contact you with the results and any needed next steps.
  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