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Immunoglobulin G (IgG) in serum/plasma 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 fight infections and is important for long-term immunity.

Quick summary

["IgG helps protect your body from infections and long-term illness by boosting immunity."]

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

Key facts at a glance

LOINC
42989-4
Short code
M pneumo IgG Titr Plr IF
Synonyms
M pneumo IgG Titr Plr IF
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Ref low
8
Ref high
61
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82977
SNOMED
3110003
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

What Does This Test Measure?

IgG is the most common type of antibody in your blood. It plays a key role in defending against bacteria and viruses, including those that cause chronic infections. Levels can vary depending on your immune response, health status, and exposure to infections.

Why Might You Need This Test?

Your healthcare provider may order this test to check for immune system function, diagnose conditions like immunodeficiency, evaluate responses to vaccines, or monitor diseases affecting antibodies, such as certain autoimmune disorders.

Common Reasons for Testing

Tests for IgG are often done when you have symptoms like frequent infections, unusual fatigue, or if you’ve had a recent illness that didn’t resolve properly. It may also be used in newborns to assess maternal antibody transfer or in people with chronic conditions like HIV or cancer.

Sample Collection and Preparation

A blood sample is taken from a vein, usually in your arm. The blood is processed to separate serum or plasma for testing. This test does not require fasting and is typically done in a lab setting.

Reference range

Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A

Specimen: fluid

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What Does a Low or High IgG Level Mean?
Low IgG levels may indicate a weakened immune system, which can make you more susceptible to infections. This could be due to genetic conditions, certain medications, or chronic illnesses. High IgG levels might suggest an overactive immune response, such as in autoimmune diseases or chronic infections.
How Often Should I Get This Test?
The frequency depends on your health condition and healthcare provider’s recommendations. Some people need this test yearly, while others may need it less often or more frequently if managing a specific health issue.
Can Diet or Lifestyle Affect IgG Levels?
Diet and lifestyle factors like nutrition, stress, and smoking can indirectly affect immune function, which may influence IgG levels. However, IgG levels are primarily determined by your body’s immune response and are not directly altered by diet alone.
  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