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IgG Immunoglobulin (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 plays a key role in long-term immunity.

Quick summary

["IgG levels help assess immune function and identify potential deficiencies or excesses."]

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

Key facts at a glance

LOINC
9456-5
Short code
Deprecated S pneum12 IgG Ser IA-aCnc
Synonyms
Deprecated S pneum12 IgG Ser IA-aCnc
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 Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like frequent infections, unusual bleeding, or if you’re being treated for an immune-related condition. It may also be checked during pregnancy to monitor fetal health or in cases of suspected immunodeficiency.

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, and a small amount of blood will be drawn. The process usually takes a few minutes.

What the Results Mean

IgG levels can vary based on age, overall health, and immune status. High levels might suggest overactive immune response or certain medical conditions, while low levels could indicate immunodeficiency or other health issues.

Common Conditions Monitored

IgG testing is often used to diagnose or monitor conditions like common variable immunodeficiency (CVID), chronic infections, or autoimmune diseases. It can also help evaluate immune responses after vaccination or treatment for immune disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

What could cause my IgG level to be low?
Low IgG levels may be due to an immune system disorder, such as CVID, or conditions that affect immune function, like certain cancers, liver disease, or long-term use of steroids. Other factors, such as malnutrition or chronic infections, can also contribute.
How do IgG levels change with age?
IgG levels naturally decline with age, but this can vary. Children and infants typically have higher IgG levels, which gradually decrease as they grow older. In adults, low IgG may signal an underlying health issue requiring further evaluation.
Can diet affect IgG levels?
While diet doesn’t directly alter IgG levels, certain nutritional deficiencies (like vitamin D, zinc, or protein) can impact immune function indirectly. A balanced diet supports overall immune health, but IgG levels are primarily determined by immune system activity.
  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