IgG Test (Immunoglobulin G)
An IgG test measures immunoglobulin G, the most abundant class of antibody in the blood. Clinicians use it to help evaluate a person's overall immune status, read in the context of history, symptoms, and any other markers ordered alongside it.
About this test
Immunoglobulin G, or IgG, is the most common antibody class circulating in the blood. It reflects the immune system's longer-term memory of substances it has encountered, and it plays a central role in the body's ongoing defenses. Because it is so widespread, IgG is often part of the picture when a clinician wants a broad view of immune function.
The IgG test is done with a simple blood draw at a Quest patient service center. A phlebotomist collects a sample from a vein, usually in the arm, and the sample goes to the laboratory. No special preparation is typically needed, though people follow any instructions their ordering clinician provides. A total IgG measurement reflects how much of this antibody class is present overall, rather than the response to any one specific substance.
Who commonly orders it
People who order an IgG test are often looking into questions about immune status, recurrent infections, or how the immune system is functioning as a whole. Others include it as part of a broader immunoglobulin panel that measures more than one antibody class at once, or because a clinician has suggested a closer look. Since IgG is read alongside other markers and interpreted against a person's history, it is rarely used to answer a question entirely on its own.
What this test looks at
This test measures the total amount of immunoglobulin G circulating in the blood. It gives a broad sense of how much of this antibody class the body carries, which is different from allergen-specific or infection-specific antibody testing that looks at the response to a particular substance.
It also helps to remember what a total IgG measurement is not. It describes the overall quantity of one antibody class rather than pinpointing a cause, which is why a clinician may read it alongside other immunoglobulin classes to build a fuller picture.
How it's often used alongside other markers
IgG is frequently measured as part of a panel that also looks at immunoglobulin A and immunoglobulin M, since each class describes a different part of the immune response. Read together, these markers offer a fuller sense of immune status than any single one can on its own. A clinician decides which combination fits the question being explored.
What to expect at your visit
No appointment is needed. People can walk into a Quest patient service center during open hours, and the draw itself is quick. A phlebotomist collects a small sample from a vein in the arm, and most visits wrap up in a few minutes. Once the laboratory completes its analysis, results are posted to the account, where they can be reviewed and shared with a clinician.
Your results
Results will be emailed securely to you as a PDF.
One-time price · physician order included · no insurance needed
Prefer a fuller panel?
A curated bundle groups this test with the markers clinicians most often review alongside it — often better value than single tests.
Frequently asked questions
What does an IgG test measure?+–
It measures the total amount of immunoglobulin G, the most abundant antibody class, circulating in the blood. This reflects how much of this antibody the body carries overall rather than the response to any one specific substance.
How is IgG different from IgA and IgM?+–
These are different antibody classes that describe different parts of the immune response. IgG is the most abundant and reflects longer-term immune memory. Clinicians often measure the classes together as a panel for a fuller view.
How is the sample collected?+–
Through a routine blood draw at a Quest patient service center. A phlebotomist takes a small sample from a vein in the arm and sends it to the laboratory.
Do I need to fast before an IgG test?+–
Fasting is not usually required, but people should follow whatever preparation instructions their ordering clinician gives, since individual situations vary and can affect how results are read.
Can an IgG result diagnose a condition?+–
No. An IgG result is a data point that a clinician interprets alongside symptoms, history, and other markers. It helps inform a conversation rather than establishing a diagnosis on its own.
How much does the IgG test cost?+–
The cash price at Celio Health is $75. That covers the physician's order and the blood draw at a Quest patient service center — no insurance is needed and there's no separate doctor's visit to pay for.