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Serum IgG Immunoglobulin Level (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.

Quick summary

["IgG antibodies fight infections and support long-term immunity."]

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

Key facts at a glance

LOINC
22563-1
Short code
S pneum IgG 1:2 Ser-Rto
Synonyms
S pneum IgG 1:2 Ser-Rto
Category
coagulation
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 Does This Test Measure?

IgG is the most abundant antibody in your blood, playing a key role in defending against bacteria, viruses, and toxins. Your body produces IgG throughout your life to provide immunity and support immune system function.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system issues, monitor immune responses, diagnose conditions like immunodeficiency, or evaluate treatment effectiveness for diseases like lupus or rheumatoid arthritis.

When Might You Get Results Back?

Results are typically available within 1 to 3 business days, depending on lab processing times. Your healthcare provider will discuss results and next steps with you.

What Can Affect This Test?

Recent infections, vaccinations, or certain medications (like steroids) can temporarily alter IgG levels. Smoking, chronic illnesses, or malnutrition may also influence results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Why do I need this test if I don’t have symptoms?
Your doctor may recommend this test as part of a routine checkup, to monitor a known condition, or to investigate unexplained symptoms like frequent infections or fatigue.
What do my IgG results mean?
Results are compared to a general range, but your doctor will interpret them in the context of your health history and other test results. They may also recommend follow-up testing if needed.
Can I eat or drink before this test?
You can eat and drink normally before this test, as it does not require fasting. Blood is drawn from a vein, usually in your arm, and the process takes about 5 minutes.
  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