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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 levels help assess immune function and detect deficiencies or excesses that may require medical attention."]

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

Key facts at a glance

LOINC
27229-4
Short code
Deprecated S pneum14 IgG Ser IA-mCnc
Synonyms
Deprecated S pneum14 IgG 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

Why This Test Is Done

Doctors may order an IgG test to evaluate immune system health, diagnose conditions like immunodeficiency, monitor treatment responses for autoimmune diseases, or check for infections in newborns or individuals with weakened immune systems.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re nervous, let your healthcare provider know—they can help make it more comfortable.

What the Test Results Mean

Results are compared to a general reference range, but individual ranges can vary. Low IgG levels may indicate immune deficiency, while very high levels could suggest certain autoimmune conditions or chronic infections.

Common Conditions Affecting IgG Levels

Conditions like HIV/AIDS, certain cancers, or long-term infections can alter IgG levels. IgG is also important in pregnancy, where it passes from mother to baby to provide temporary immunity.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What causes IgG levels to be low?
Low IgG levels can result from primary immune deficiencies, chronic illnesses (like HIV or cancer), malnutrition, or certain medications. It’s also common in newborns, as their immune system develops.
How often should IgG levels be checked?
Your doctor will determine how often you need testing based on your health history, symptoms, and treatment plan. Regular monitoring may be needed if you have an immune disorder or take medications that affect immunity.
Can IgG levels change with diet?
Diet can indirectly affect immune function, but IgG itself is produced by the body’s immune cells. While a balanced diet supports overall health, it doesn’t directly alter IgG levels unless underlying conditions (like malnutrition) are present.
  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