If you think you have Hepatitis B, or think you have been exposed to Hepatitis B, see a doctor and get tested. If you've already had the vaccine, ask your doctor if you should consider updating it by getting a booster vaccine.
For women:
If you are pregnant, you should get tested at your first prenatal visit. If your doctor thinks you are at higher risk for getting Hepatitis B, they may recommend getting tested again during your third trimester.