Immunoassay for Immunoglobulin G (IgG) Substance Concentration in Serum or Plasma

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like frequent infections, low energy, or if you’re being evaluated for conditions like immunodeficiency, chronic diseases, or after receiving certain treatments that can affect immune function.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if your blood is drawn early in the morning. Wear comfortable clothing and plan to stay near the testing site for a short time.

How the Test Is Performed

A healthcare professional will draw blood from a vein in your arm using a small needle. You may feel a brief pinch, but it usually doesn’t cause discomfort afterward. The blood sample is then sent to a lab for analysis using an immunoassay method to detect IgG levels.

What the Results Mean

Results are typically reported as a concentration value (e.g., grams per liter). Lower than expected levels may indicate weakened immunity, while higher levels could suggest chronic infections, autoimmune conditions, or other health concerns. Your provider will interpret results in the context of your overall health.