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Immunoassay for Immunoglobulin G (IgG) in serum/plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of Immunoglobulin G (IgG), a key protein in your immune system, found in your blood.

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
95540-1
Short code
CREIMP-VIM
Synonyms
blaIMP+blaVIM Islt/Spm Ql
Category
chemistry
Sample
serum
Container
Sterile, leak-proof container or appropriate transport medium; for serum samples, use serum separator tube (SST) or red-top vacutainer tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
molgen
CPT
87150 (if culture-based identification) or 87798 (for direct molecular probe detection); may also use 87799 with appropriate modifier
SNOMED
43461000119103
Specimen volume
1-2 mL of serum or appropriate sample volume per institutional protocol (typically 1 mL minimum for molecular testing)
Stability
Refrigerate at 2-8°C if testing within 48 hours; otherwise freeze at -70°C or below. Avoid repeated freeze-thaw cycles. Transport at 2-8°C with cold chain maintenance.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Does IgG Measure?

IgG is one of the most abundant antibodies in your blood. It plays a crucial role in defending against bacteria and viruses, as well as helping your body remember past infections. Levels can vary based on your immune response, overall health, and exposure to infections.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate immune responses to vaccines, or monitor diseases affecting the immune system, such as certain cancers or autoimmune disorders.

How Is the Test Performed?

A small blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is analyzed using an immunoassay method to measure IgG levels.

What Are Common Reasons for Testing?

Common reasons include assessing immune function, diagnosing conditions like HIV, evaluating responses to vaccines, or checking for deficiencies in antibody production.

Reference range

Negative (No blaIMP or blaVIM carbapenem resistance genes detected). A positive result indicates the presence of one or both metallo-beta-lactamase genes associated with carbapenem resistance.N/A

Specimen: serum

No fasting required. Specimen should be collected prior to initiation of antimicrobial therapy when possible. Avoid contamination during collection. Patient should be informed that this test detects genetic resistance markers and results will guide appropriate antibiotic therapy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

IgG levels can be lower in people with certain immune deficiencies, chronic illnesses, or those who have had severe infections. High levels may sometimes indicate chronic infections, certain autoimmune diseases, or overactive immune responses. However, individual results depend on overall health and medical history.

Short name

IgG Level

Frequently asked questions

What does an abnormal IgG level mean?
An abnormal IgG level may suggest an underlying health issue, such as a weakened immune system, chronic infection, or an autoimmune condition. Your doctor will discuss results in the context of your symptoms and medical history.
How often should I get this test?
The frequency depends on your medical condition and reasons for testing. Your healthcare provider will determine the best timing based on your individual needs.
Can diet or lifestyle affect IgG levels?
While diet and lifestyle can influence overall immune health, IgG levels are primarily determined by your immune system’s response. Specific dietary changes may not directly alter IgG test results, but maintaining a balanced diet supports immune function.
  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