Many people with hepatitis B have no symptoms so a diagnosis is based on blood tests. These tests include:

• Hepatitis B surface antigen (HBsAg). This test looks for a protein that is present on the outside of the HBV called the hepatitis B surface antigen. If you are infected with HBV either acutely or chronically you will test positive on this test. A negative test means you are probably not infected.
• Antibody to hepatitis B surface antigen (anti-HBs). This test determines if your immune system has produced antibodies against HBsAg. A positive result for these antibodies means you have had prior exposure to HBV either by infection or vaccination. In either case you probably cannot infect others or become infected yourself because you’re protected by these antibodies.
• Antibody to hepatitis B core antigen (anti-HBc). This test looks for antibodies directed against a protein normally found inside the HBV virus called the core antigen (HBc). A positive test indicates that you may have a chronic infection that you can transmit to others but some people who are recovering from an acute infection or who have cleared the virus may also test positive.  

To confirm a diagnosis of hepatitis B, the doctor may want to examine your liver. This can be done using an X-ray, ultrasound, or CT scan but the most accurate method is a liver biopsy. A biopsy involves removing a small piece of liver with a needle and examining it under a microscope for signs of disease. People with chronic disease may show a wide range of liver damage on biopsy. Some people who test positive for chronic disease based on blood work may have little or no liver inflammation or damage at all. These people are considered carriers and may never develop any symptoms of the disease. For others, the amount of inflammation and damage present determines the prognosis for the disease; greater levels of inflammation, fibrosis, and cirrhosis are associated with poorer outcomes.