Serum or Plasma Substance Concentration (Mass Concentration) for Immunoglobulin G (IgG) – Quantitative

What Does This Test Measure?

IgG is the most common type of antibody in your blood. It plays a key role in defending against bacteria and viruses. This test helps doctors assess your immune system’s ability to fight infections and provides information about conditions like immune deficiencies, chronic infections, or autoimmune diseases.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of a weakened immune system, such as frequent infections, unexplained fatigue, or if you’re being treated for conditions like lupus, rheumatoid arthritis, or HIV. It may also be used to monitor immune responses during treatments like chemotherapy or for newborns to check for maternal antibodies.

What to Expect Before the Test

No special preparation is usually needed. You may have a small needle inserted into your arm or vein to draw blood. If you’re having a 24-hour urine test (if applicable), you’ll need to collect urine samples over a full day. Always follow your provider’s instructions.

What to Expect During the Test

The blood draw is quick and typically painless. If you’re uncomfortable, let your healthcare provider know. If this is a urine test, you’ll need to follow specific collection guidelines to ensure accurate results.