Serum or Plasma IgG Substance Concentration (Qualitative or Quantitative)

What IgG Tests Measure

IgG tests determine the concentration of IgG antibodies in your blood, either as a screening or confirmatory test. The method used may vary, but it often involves detecting the presence or level of IgG through techniques like immunoassay or nephelometry. This helps assess immune function, diagnose conditions like immunodeficiency, or monitor treatment responses.

Why It Matters in Your Health

IgG levels can indicate whether your immune system is functioning properly. Low levels may suggest immune deficiencies, while abnormal levels could point to infections, autoimmune diseases, or other health issues. Your doctor may order this test if you have frequent infections, unexplained fatigue, or symptoms of immune disorders.

When You Might Need This Test

You might need an IgG test if you have symptoms like repeated infections, slow wound healing, or if your doctor suspects an immune-related condition. It’s also used in newborns to check for maternal antibodies passed during pregnancy or after birth.

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 it involves a blood draw. Wear comfortable clothing and arrive with an ID for easy access to your medical records.