Yes, you can be exposed to hepatitis B by having sex with someone infected with the hepatitis B virus. In fact, sexual
contact is how most adults in the United States probably get infected.
The hepatitis B virus spreads by direct contact with infected blood. However, it's also spread by contact with semen, vaginal fluids and other body fluids. This means that in addition to sharing things like needles and syringes, you can also get hepatitis B by having sex with an infected partner.