Hepatitis B: Symptoms, Causes, Testing and Treatment

What is Hepatitis B?

Hepatitis B is a viral infection that affects the liver — the hepatitis B virus (HBV). The virus is found in blood and bodily fluids such as semen, which is why it’s classified as a sexually transmitted infection (STI). While hepatitis B can cause serious health problems, it is preventable and treatable.

How do you get hepatitis B?

Hepatitis B is most commonly spread through unprotected sex with someone who is infected. It can also be transmitted through contact with infected blood or bodily fluids. To lower your risk of hepatitis B, it's important to practise safe sex, especially if you’re unsure of your partner’s medical history.

For those at higher risk, the NHS offers a hepatitis B vaccine, which is an effective way to prevent infection.

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Symptoms of Hepatitis B

Not everyone with hepatitis B experiences symptoms, and some people may fight off the infection without even knowing they had it. However, if symptoms do appear, they usually develop one to three months after being infected.

Symptoms of hepatitis B can feel similar to the flu or a bad stomach bug, and may include:

  • Fever

  • Aches and pains

  • Nausea and vomiting

  • Diarrhoea

  • Abdominal pain

  • Loss of appetite

  • Jaundice: Yellowing of the skin and eyes

  • Dark urine

  • Pale stools

If you notice these symptoms, it’s important to get tested.

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Testing for Hepatitis B

If you believe you may have been exposed to hepatitis B or are experiencing symptoms, it’s crucial to get tested, some providers even offer a free hepatitis B test or hepatitis B home test. You can visit your GP or a sexual health/GUM clinic for a blood test to check for the virus. Testing is especially important if you’re at higher risk, such as if you’ve had unprotected sex or are in a high-risk group.

If you’ve recently been exposed to the virus, emergency treatment may be available to prevent infection. Ideally, this should be given within 48 hours of exposure for the best chance of preventing hepatitis B.

Frequently asked questions

Here are direct answers to some of the most frequently asked questions about hepatitis B.

Hepatitis B test results are usually described using a set of markers rather than a simple positive or negative. HBsAg (hepatitis surface antigen) shows whether the virus is currently present — someone who is HBsAg-positive currently has the virus — while anti-HBs shows immunity, either from past infection or from being vaccinated (immunised). Anti-HBc and HBeAg or anti-HBe help doctors work out whether an infection is active or inactive. Your results, alongside your genotype, help a clinician decide whether you need treatment now or ongoing monitoring.

Acute hepatitis B is a short-term infection that most adults clear on their own within a few months, often becoming seropositive for immunity afterwards. In rare cases, acute infection progress very rapidly and needs urgent care. Chronic hepatitis B means the virus hasn’t cleared and continues to replicate, mutate and, in some cases, integrate into liver cells over time. During this replicative phase the virus can also gradually develop into a lifelong condition — this is why regular monitoring matters, even if you feel well.

In some people, ongoing chronic infection can cause scarring of the liver, known as liver fibrosis, which can lead to cirrhosis (late stage liver disease with severe scarring throughout the liver).  In a small number of cases, this raises the risk of hepatocellular carcinoma (HCC), where liver cells carcinogenise into a form of liver cancer. This is why screening and helping clinicians diagnose the condition early matter so much.

Treatment aims to suppress the virus rather than necessarily cure it. Antiviral medications work by helping to regulate, deactivate or modulate viral activity, while interferon treatments help activate your own immune response, so the virus becomes suppressed and stays at low levels. 

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