Serum Immunoassay for Immunoglobulin G (IgG) Substance Concentration

Why This Test Might Be Ordered

Your healthcare provider may order an IgG test to check for low or high levels, which can happen due to immune system conditions, infections, or certain medical treatments. It’s also used to monitor immune responses, especially in people with weakened immune systems or chronic illnesses like HIV or autoimmune diseases.

What to Expect Before the Test

No special preparation is needed for this blood test. You may be asked to fast for a few hours before the draw, but this depends on your provider’s instructions. Bring any medications you’re taking to your appointment.

What the Test Results Mean

Results are compared to a general reference range, but individual ranges can vary. Low IgG levels may indicate a weakened immune system, while very high levels could suggest certain immune disorders or overactive immune responses. Your provider will discuss results in the context of your health history.

Common Reasons for Testing

IgG tests are often done to diagnose or monitor conditions like chronic infections, autoimmune diseases (e.g., lupus), or immune deficiencies. They’re also used in newborns to check for maternal antibodies passed during pregnancy.