Total Immunoglobulin G (IgG) Concentration

What IgG Is and Its Role in Your Body

IgG is the most abundant antibody in your blood and plays a critical role in defending against pathogens like bacteria and viruses. It circulates in your bloodstream and provides long-term immunity by helping your immune system remember past infections. Low levels of IgG can increase your risk of frequent infections, while high levels may be associated with certain autoimmune conditions or chronic inflammation.

When You Might Need This Test

Your doctor may order an IgG test if you have frequent or recurring infections, symptoms of an immune deficiency, or if you’re being evaluated for conditions like HIV, lupus, or other autoimmune diseases. It’s also sometimes checked in newborns to assess their immune system development or in people with chronic illnesses like cancer or kidney disease.

How the Test Works

Blood is drawn from a vein in your arm, and the sample is analyzed to measure the concentration of IgG antibodies. The test typically uses a blood sample and may be performed in a lab using methods like nephelometry or immunoturbidimetry to detect and quantify IgG levels accurately.

What to Expect Before the Test

There are usually no special preparations needed for this test. You may be asked to fast before the test if it’s part of a larger panel, but for IgG alone, eating or drinking normally is fine. Wear comfortable clothing and let your doctor or phlebotomist know if you have any concerns about needles or blood draws.