Hepatitis B
A viral infection of the liver caused by the hepatitis B virus, spread through blood and bodily fluids. Many acute infections clear on their own, but some become chronic and, over years, can damage the liver. It is preventable by vaccination and, when chronic, very treatable — living well with it is the norm.
What it is
Hepatitis B is an infection of the liver caused by the hepatitis B virus (HBV). It spreads through contact with infected blood and bodily fluids — for example from mother to baby at birth (a major route worldwide), through sexual contact, or through shared needles. After infection it can follow two courses. An acute infection may cause a flu-like illness with tiredness, nausea, poor appetite and sometimes jaundice (yellowing of the skin and eyes) and dark urine — though many people, especially children, have no symptoms at all. In most healthy adults the immune system clears the acute infection within a few months, leaving lifelong immunity. In some people, particularly those infected as babies or young children, the virus is not cleared and the infection becomes chronic (long-standing). Chronic hepatitis B is often silent for years but, in a proportion of people, slowly inflames and scars the liver, which over decades can lead to cirrhosis and a raised risk of liver cancer. It is diagnosed and characterised through a panel of blood markers — the surface antigen, core and surface antibodies, viral load and liver tests. Crucially, hepatitis B is preventable by a safe, effective vaccine, and chronic infection is well controlled by modern antiviral medicines, so people with it live full lives with monitoring and, when needed, treatment.
Key lab markers
- Hepatitis B surface antigen (HBsAg) — positive in active infection; still positive after six months means chronic infection.
- Hepatitis B core antibody (anti-HBc) — marks genuine exposure; the IgM form points to a recent (acute) infection.
- Hepatitis B surface antibody (anti-HBs) — marks immunity, from a cleared infection or vaccination.
- HBV DNA (viral load) — measures how much virus is present; guides treatment.
- ALT and AST — liver enzymes; raised when the liver is inflamed.
- HBeAg and other markers — help gauge activity and infectiousness.
Symptoms
- Often none, especially in chronic infection
- Tiredness and a general feeling of being unwell
- Nausea, poor appetite
- Pain or discomfort under the right ribs (over the liver)
- Jaundice — yellowing of the skin and eyes
- Dark urine and pale stools
- Joint aches
- In long-standing disease with liver damage: swelling, easy bruising, and other signs
Related symptoms
Related lab panels
When to discuss with a doctor
A positive hepatitis B test is a reason to see a doctor, not a reason to panic — it opens the way to effective, straightforward care. The steps are further blood tests to work out whether the infection is acute or chronic and how active it is, liver assessment, and advice on protecting close contacts, who can be vaccinated. Many people with chronic hepatitis B stay well and simply need regular monitoring of the liver; when the infection is more active, antiviral tablets control it very effectively and reduce the long-term risks. In pregnancy, identifying hepatitis B lets the baby be protected at birth. Vaccination prevents the infection entirely and is recommended for those at risk. Seek prompt care for jaundice, severe vomiting or feeling very unwell during an acute infection. Mediora.AI can flag the hepatitis B marker and liver-test pattern that points to the infection; confirming the picture and planning monitoring or treatment belong with your doctor.