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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 antibodies fight infections and support immunity over time."]

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

Key facts at a glance

LOINC
86090-8
Short code
S pneum Da 3 IgG 2:1 Ser-Rto
Synonyms
S pneum Da 3 IgG 2:1 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 common type of antibody in your blood. It plays a key role in defending against bacteria and viruses, including those that cause chronic infections. Your body produces IgG in response to vaccines, infections, and exposure to foreign substances.

Why Might You Need This Test?

Doctors may order an IgG test to check for low or high levels, which can happen due to immune system issues, certain diseases, or after treatments like chemotherapy. It’s also used to monitor immune responses, especially in people with weakened immune systems.

When Might You Get This Test?

You might have this test if you have symptoms like frequent infections, unexplained fatigue, or if your doctor suspects an immune disorder. It could also be part of a routine checkup or before certain treatments that affect immunity.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re nervous, let your doctor or phlebotomist know so they can help make it more comfortable.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels can be lower in people with immune deficiencies, autoimmune diseases (like lupus or rheumatoid arthritis), or after treatments that weaken the immune system. High levels may suggest chronic infections, certain cancers, or overactive immune responses.

Short name

IgG Level

Frequently asked questions

What Are My IgG Levels Telling Me?
Your IgG levels are compared to what’s typical for healthy adults. If your results are outside the expected range, your doctor will discuss what that might mean for your health and next steps.
How Often Should I Get This Test?
The frequency depends on your health and why the test was ordered. Your doctor will let you know how often to get it checked, especially if you have a condition that affects IgG levels.
Can I Eat or Drink Before This Test?
You can eat and drink normally unless your doctor tells you otherwise. Avoiding alcohol or caffeine before the test might help, but it’s best to follow your doctor’s instructions.
  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