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 found 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
47331-4
Short code
Deprecated S pneum20 IgG Ser IA-mCnc
Synonyms
Deprecated S pneum20 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

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 based on your immune response, overall health, and exposure to infections or vaccines.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system issues, such as low immunity (immunodeficiency), infections, or conditions like lupus or rheumatoid arthritis. It can also help monitor treatment effectiveness for certain diseases.

When Might You Get This Test?

You might have this test if you have symptoms like frequent infections, fatigue, or if your doctor suspects an immune disorder. It’s sometimes done as part of a routine check-up or before certain treatments.

What to Expect Before the Test

No special preparation is usually needed. You’ll have a small needle inserted into your arm to draw blood. It only takes a few minutes, and you can return to normal activities afterward.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: IgG Levels Can Indicate Immune Function or Disease

Short name

IgG Level

Frequently asked questions

How Long Will Results Take?
Results are typically available within 1–3 business days, depending on your lab. Your doctor will discuss the results with you.
What Are Normal IgG Levels?
Normal IgG levels vary by age and health. Your doctor will compare your results to your specific reference range and explain what they mean for you.
Can Diet or Supplements Affect IgG Levels?
Diet and supplements generally don’t directly affect IgG levels, but maintaining a balanced diet supports overall immune function. If you’re taking supplements, check with your doctor first.
  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