The Hepatitis B Surface Antigen (HBsAg) Qualitative test is a key blood test for detecting an active Hepatitis B infection. It identifies the presence of HBsAg, a protein on the surface of the virus, showing whether the virus is currently in your body. A simple blood draw allows the lab to provide a clear positive or negative result. This test is essential for diagnosing infection, monitoring potential exposure, and guiding your doctor on further evaluation or treatment. By confirming the presence of the virus, it delivers critical, actionable information to help protect your liver health.