Serum IgG Substance Concentration (Mass Concentration)

What Is Immunoglobulin G (IgG)?

IgG is the primary antibody produced by your immune system to fight off bacteria and viruses. It’s found in high levels in your blood and provides long-term immunity. Low IgG levels may indicate a weakened immune response, while elevated levels could suggest chronic infections or certain autoimmune conditions.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It’s also used in diagnosing conditions like HIV, certain autoimmune diseases, or before receiving immune-modifying treatments.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate serum (the liquid part without clots) for testing. This test does not require fasting or special preparation beyond standard blood draw procedures.

What to Expect Before or After the Test

You may experience mild discomfort or bruising at the injection site, but most people tolerate blood draws well. If you have a history of bleeding disorders or take blood thinners, let your doctor know to ensure safe testing. Results are typically available within 1–3 business days.