Serum IgG Substance Concentration (Immunoglobulin G)

What Does IgG Measure?

IgG is the most abundant antibody in your blood and plays a crucial role in defending against bacteria and viruses. It’s produced by your immune system to help protect you from infections and chronic diseases. Levels can vary depending on your health status, immune response, and exposure to pathogens.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate responses to vaccines, or monitor diseases such as lupus or multiple sclerosis. It can also help assess how well your body is producing antibodies after an infection or vaccination.

Common Reasons for Testing

Common reasons include identifying immune deficiencies, evaluating vaccine responses, diagnosing autoimmune diseases, or checking for infections where IgG antibodies are involved. It’s sometimes used in newborns to assess maternal antibody transfer or in chronic illnesses like HIV.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw if your doctor specifies it. Wear a loose shirt for easy access, and bring any medications you’re currently taking to discuss with your healthcare provider.