Basics

What Is Hepatitis B?

This introduction explains what hepatitis B is, how it affects the liver, and why basic understanding matters before any testing or vaccine decision.

Medical reviewer

Dr. Aaron Patel, MD

Reviewed

April 20, 2026

Reading time

1 min read

Hepatitis B is a viral infection that affects the liver. Some infections are short term, while others can become long lasting and raise the risk of serious liver problems over time. That is one reason the topic belongs in ordinary preventive care, not only in high-drama medical moments.

The virus can spread through blood and certain body fluids, which means many people first hear about it through vaccine conversations, screening questions, or exposure concerns. A person does not need to feel obviously ill for hepatitis B to matter. Sometimes the most important step is simply understanding what the term means and why a clinician is asking about it.

Start with the basics

If someone understands that hepatitis B is a liver infection, that it can be prevented with vaccination, and that testing can answer status questions, they already have the core of the issue. From there, the next step becomes much easier to navigate.

Sources

  1. CDC: Hepatitis B basics
  2. World Health Organization: Hepatitis B fact sheet
  3. NIDDK: Definition and overview of hepatitis B