The Full form of HBSAG is Hepatitis B Surface Antigen. HBsAG is a blood test ordered to determine if someone is infected with the hepatitis B virus. If it is found, along with specific antibodies, it means the person has a hepatitis B infection. If a person’s blood is positive for HBsAg, it means he is infectious for the virus and can pass it to other people through his blood or body fluids. Hepatitis B caused by the hepatitis B virus (HBV) and is a serious liver infection. Having chronic hepatitis B increases your risk of developing liver cancer, liver failure or cirrhosis—a condition that causes permanent scarring of the liver. Most adult people infected with hepatitis B recover fully, even if their signs and symptoms are severe. Infants and children are more likely to develop a chronic hepatitis B infection. A vaccine can prevent hepatitis B, but there’s no cure if you have it. Signs and symptoms of hepatitis B, ranging from mild to severe, usually appear about 1 to 4 months after you’ve been infected. They may include abdominal pain, Dark urine, Fever, Joint pain, Loss of appetite, Nausea and Vomiting, Weakness and Fatigue, Yellowing of your skin and the whites of your eyes (jaundice).