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Immunoglobulin G (IgG) in Serum or Plasma (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 is the most common antibody found in the blood.

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
15184-5
Short code
IgG Ser Ql IEP
Synonyms
IgG Ser Ql IEP
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immunoelectrophoresis
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 Is Immunoglobulin G (IgG)?

IgG is the primary antibody your immune system produces to fight bacterial and viral infections. It circulates in your bloodstream and provides long-term immunity. Low IgG levels may indicate a weakened immune response, while high levels could suggest chronic immune activation or certain medical conditions.

Why Might You Need This Test?

Doctors order IgG tests to diagnose or monitor conditions like immune deficiencies (e.g., common variable immunodeficiency), chronic infections, autoimmune diseases, or to evaluate immune responses after vaccination or treatment for infections.

When Could You Expect Results?

Results are typically available within 1 to 3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the results with you during your follow-up visit.

Common Reasons for Testing

Common reasons include recurrent infections, unexplained fatigue, autoimmune diseases, or if you’re being treated for an immune-related condition. Some children with developmental delays or frequent ear infections may also be tested for IgG levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

How long does it take for IgG levels to change after a vaccination?
IgG levels can take weeks to months to fully develop after vaccination, depending on the vaccine and your immune response. Some people may see a rise in IgG within 2–4 weeks, while others may take longer. Your doctor can track changes over time during follow-up visits.
Can IgG levels be affected by diet or supplements?
Dietary factors like vitamin D, zinc, or protein intake may indirectly support immune function, but they don’t directly influence IgG levels. Supplements (e.g., immune-supportive herbs) may have limited impact unless prescribed by a healthcare provider.
What should I do if my IgG levels are low?
If your IgG levels are low, your doctor may recommend further testing to rule out underlying causes (e.g., malabsorption, autoimmune conditions) or suggest immune-modifying therapies, such as intravenous immunoglobulin (IVIG) treatments, if needed. Follow-up visits will guide next steps.
  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