Your doctor may use a variety of tests to check your liver and monitor the virus in your body. The following list provides brief descriptions of these tests and what they measure. It's important to monitor the health of your liver with these tests because the virus can silently cause damage. You may feel fine, but your liver may still be at risk. If you have questions or want to know more about any of these tests, consult your doctor.

Blood tests to monitor the virus in your body:

• HBsAg: Hepatitis B surface antigen is part of the hepatitis B virus that is found in the blood of someone who is infected. If this test is positive, then the hepatitis B virus (HBV) is present, indicating either acute (if present for less than six months) or chronic HBV infection (if present for at least six months).
• HBsAb (or anti-HBs): Hepatitis B surface antibody is formed in response to the hepatitis B virus or vaccine. If this test is positive, it means the immune system has successfully developed a protective antibody against HBV. Someone who is surface antibody positive is considered immune to HBV, and cannot pass the virus on to others.
• HBcAb (or anti-HBc): Hepatitis B core antibody does not provide any protection or immunity against the hepatitis B virus. A positive test indicates that a person may have been exposed to the hepatitis B virus.
• HBeAg: Hepatitis B "e" antigen is a protein that is present when the hepatitis B virus is actively reproducing in people with certain strains of HBV. This test is used to monitor the effectiveness of some treatments for chronic HBV infection.
• HBV DNA: A test that directly measures the amount of hepatitis B virus in the blood (called "viral load"). This test is often used to help determine if treatment is necessary and monitor the effectiveness of treatment.

Blood tests to monitor the health of your liver:

• Bilirubin: A yellow fluid produced in the liver when worn-out red blood cells are broken down. Bilirubin can leak out from the liver into the bloodstream if the liver is damaged. When bilirubin builds up, it can cause jaundice — a yellowing of the eyes and skin, dark urine and light-colored stool.
• Albumin: A protein made in the liver that is the main protein present in human blood. If the liver is badly damaged, it can no longer produce normal amounts of albumin. Very low levels of albumin may be a sign of liver damage.
• Prothrombin Time (PT): A test that measures how much time it takes for a person's blood to clot. Prothrombin is a protein made in the liver that helps blood to clot. When the liver is significantly injured, prothrombin may not be produced in normal amounts. This can result in a longer PT.
• Alpha-fetoprotein (AFP): This test looks for high levels of AFP, a protein that is produced by cancerous liver cells, and is useful in the screening and diagnosis of liver cancer. Because people with chronic hepatitis B are at an increased risk of liver cancer, this test is usually performed every six to 12 months.
• Alanine aminotransferase(ALT): Also called SGPT. ALT is an enzyme found in liver cells that can leak out into the bloodstream when liver cells are damaged. An elevated ALT level can indicate that the liver is inflamed and there is a risk of permanent liver damage.

Other diagnostic tests to monitor the health of your liver:

• Ultrasound: A test used to screen for liver cancer in people with chronic hepatitis B by examining the shape, size and appearance of the liver. An ultrasound is painless and usually takes no more than 10 to 15 minutes to conduct. You may need to make an appointment at a facility that specializes in diagnostic procedures for this test. An ultrasound takes pictures of your liver using sound waves. The person performing the exam runs a special "probe" along your abdomen. The probe sends out sound waves that bounce back to a computer. The computer then generates pictures of your liver. Some experts recommend an abdominal ultrasound every six to 12 months.
• Liver biopsy: A procedure in which tissue samples from the liver are removed to help determine the presence and extent of liver damage. A liver biopsy is generally considered minor surgery, so it may done at the hospital. For the biopsy, you will lie on your back with your right hand above your head. After marking the outline of your liver and injecting a local anesthetic to numb the area, the doctor will make a small incision in your right side near your rib cage. Your doctor then inserts the biopsy needle and retrieves a sample of your liver tissue. You may feel pressure or dull pain, but otherwise the procedure causes minimal discomfort. You're often done in just 20 minutes, but your doctor may ask that you stay at the hospital or office to be monitored for an hour or two afterwards. You also may need to take it easy for up to 12 hours after the procedure. The area where the doctor inserted the needle may be sore for up to a day. Like any minor surgery, a liver biopsy does have some risks (like infection or bleeding), but these complications are rare.

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