There are three blood tests for Hepatitis B. One tests for the virus itself, and two test for your body’s reaction to the virus. Sometimes your healthcare provider will do all three tests, since they tell her different things.
- If you are positive for the antigen test (HBsAg) it means that you are currently infected with the virus and can pass it to other. If you clear an HBV infection, and do not remain chronically infected, you will usually test negative again within 4 months after your symptoms resolve.
- If you are positive on the anti-HBs test, which looks for your body’s reaction to a surface protein of the virus, it means that you are immune to Hepatitis B. This could either be because you were previously exposed to the virus or because you were vaccinated. You can not pass the virus to others.
- If you are positive on the anti-HBc test, which looks for your body’s reaction to a core protein of the virus, it usually means that you are chronically infected with HBV, and can pass the disease to others. However, if you are also positive on the anti-HBs test, then a positive anti-HBc test is probably because of a previous infection.
Other tests may be ordered if your doctor thinks you are chronically infected with HBV. These tests are done to monitor the progress of the disease and its treatment - not to detect whether or not you are infected.
There is a vaccine for hepatitis B. If you are at high risk for the disease, you should talk to your doctor about getting vaccinated. Risk factors include: multiple sex partners, a sexual partner with HBV, living with someone with chronic HBV, a job that brings you in contact with human blood, injection drug use, and being a man who has sex with men.