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Serum Immunoglobulin G (IgG) Level

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 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
14205-9
Short code
C immitis Ag Islt Ql ID
Synonyms
C immitis Ag Islt Ql ID
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-diffusion
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 your body against bacteria and viruses. This test helps doctors assess your immune system’s ability to produce antibodies and monitor conditions that affect immunity, such as certain infections or immune disorders.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms of a weakened immune system, such as frequent infections, slow healing wounds, or unexplained fatigue. It can also be used to monitor conditions like HIV, lupus, or other autoimmune diseases, or to check for immune deficiencies in newborns or infants.

Common Reasons for Testing

Doctors may also use this test to evaluate immune responses before vaccines, to diagnose or monitor immune-related diseases, or to check for conditions like chronic infections or certain cancers that affect antibody production.

Sample Collection and Preparation

A blood sample is taken from a vein in your arm. You may feel a small pinch when the needle is inserted, but the procedure is quick and usually painless. The blood is then sent to a lab for testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How low or high might my IgG levels be?
IgG levels can vary based on age, overall health, and medical conditions. Low IgG levels may suggest an immune deficiency, while very high levels might indicate certain immune disorders or chronic infections. Your doctor will interpret the results in the context of your health history and symptoms.
What do my results mean?
If your IgG levels are outside the expected range, your doctor may recommend further testing or treatments to address potential immune issues. Results alone don’t diagnose a condition—they help guide next steps in your care plan.
Can I prepare for this test?
No special preparation is needed for this blood test. You can eat and drink normally on the day of your appointment, but let your doctor know if you’re taking any medications that might affect blood tests.
  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