Making the Diagnosis
Both hepatitis A and B are diagnosed by taking a blood sample, which will be sent to a lab to determine if you have antibodies in your blood specific for those viruses. If you do, then you have been exposed to hepatitis A or B.
In hepatitis B, the lab will also examine whether your blood contains any hepatitis B antigens (proteins on the surface of the virus that help your immune system recognize infections).
Along with blood tests and other tools (e.g., liver enzyme and function tests), your doctor will do a physical examination and ask you questions about your symptoms to make a diagnosis.