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Immunoglobulin G (IgG) in Serum/Plasma

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 plays a key role in long-term immunity.

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
94875-2
Short code
Nuclear IgG SerPl IA-aCnc
Synonyms
Nuclear IgG SerPl IA-aCnc
Category
chemistry
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

Why This Test Is Done

Doctors may order an IgG test to evaluate your immune system, especially if you have recurrent infections, chronic illnesses, or conditions like HIV/AIDS, lupus, or certain autoimmune diseases. It can also be used to monitor treatment responses in patients with immune-related disorders.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw a blood sample. If you’re on blood thinners, let your healthcare provider know before the test.

What the Test Results Mean

IgG levels vary depending on age, overall health, and medical conditions. While reference ranges can differ by lab, low IgG levels may indicate immune system weakness, while very high levels could suggest overactive immune responses or certain diseases.

Common Conditions Linked to IgG Levels

Low IgG levels may be linked to conditions like common variable immunodeficiency (CVID), severe combined immunodeficiency (SCID), or malnutrition. High IgG levels can be seen in chronic infections, certain cancers, or autoimmune diseases like rheumatoid arthritis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG Level

Frequently asked questions

Will my IgG test results affect my treatment?
Your healthcare provider will interpret your IgG results in the context of your overall health, symptoms, and medical history. If results are outside normal ranges, further testing or treatment adjustments may be recommended to address potential immune issues.
Can I still eat or drink before the test?
Yes, you can eat and drink normally before the blood draw, unless your doctor has specific instructions otherwise. Avoiding alcohol or caffeine for a few hours before the test may help ensure accurate results.
How long will it take to get my IgG test results?
Test results are typically available within 1 to 3 business days, depending on your lab. Your doctor will discuss the findings with you during your follow-up visit.
  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