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Immunoglobulin G (IgG) in Serum (Quantitative)

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 diseases.

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
43853-1
Short code
L pneumo 1+3+4+5+6+8 IgM Ser Ql
Synonyms
L pneumo 1+3+4+5+6+8 IgM Ser Ql
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 Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. Antibodies are proteins that help your immune system recognize and fight off harmful substances like bacteria and viruses. IgG is particularly important because it can cross the placenta to provide protection to your baby during pregnancy. It also plays a role in long-term immunity by remembering past infections to help your body respond faster if you encounter the same pathogen again.

Why Might You Need This Test?

Doctors may order an IgG test to check for low or high levels, which can indicate conditions such as immune deficiencies, infections, or certain autoimmune diseases. It’s also used in monitoring immune responses, especially in newborns, infants, or people with weakened immune systems.

When Could You Expect Results?

Test results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the results with you and explain what they mean for your health.

What Does IgG Tell Us About My Health?

Low IgG levels might suggest an immune system that isn’t working as well as it should, which can increase your risk of infections. High IgG levels could indicate chronic infections, certain autoimmune conditions, or even allergic reactions. Your doctor will use the results alongside other tests and symptoms to determine the best course of action.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How is the IgG test performed?
A blood sample is taken from a vein in your arm. The blood is then sent to a lab where it is processed to separate the serum (the liquid part without blood cells). The lab uses a specialized immunoassay method to measure the amount of IgG in your serum.
Will I feel any discomfort during the blood draw?
You might feel a slight pinch or sting when the needle is inserted, but most people describe it as mild discomfort. Afterward, you may have a small bruise or swelling at the site, but this usually goes away quickly. If you’re nervous, let your healthcare provider know—they can offer ways to make it more comfortable.
Can I eat or drink before this test?
You can usually eat and drink normally before this test unless your doctor has specific instructions. Some tests may require fasting, but IgG tests do not. Always follow your doctor’s or lab technician’s instructions for the best 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