When you start PrEP, the clinic tests you for hepatitis B as well as HIV. It can seem like an odd extra, but there is a good reason. The medicines in PrEP pills also act against the hepatitis B virus, and that has consequences for starting and, especially, for stopping.
Why PrEP pills also act on hepatitis B
Both PrEP pills contain emtricitabine with a form of tenofovir: tenofovir disoproxil fumarate (TDF) in Truvada, and tenofovir alafenamide (TAF) in Descovy. The UK guideline notes that both combinations are active against hepatitis B1.
In fact, tenofovir on its own is a standard hepatitis B treatment. Viread (TDF) is approved to treat chronic hepatitis B as well as HIV, and Vemlidy (TAF) is approved to treat chronic hepatitis B34. Truvada itself is approved for HIV treatment and PrEP, not as a hepatitis B treatment2.
The hepatitis B test before PrEP, and the vaccine
The Truvada label says everyone should be tested for hepatitis B before or when starting2. The UK guideline adds some practical detail1:
- PrEP pills can be started while the hepatitis B result is awaited, but the result should be checked as soon as possible.
- If you have no sign of current or past infection and are not immune, you should be offered the hepatitis B vaccine.
- People at ongoing risk who have not been vaccinated should have a hepatitis B blood test every year.
The Truvada label also says people without hepatitis B should be offered vaccination2. PrEP is not a substitute for the vaccine.
If you have hepatitis B
Having hepatitis B does not stop you using PrEP. But it changes how it is managed. The UK guideline recommends1:
- Referral to a specialist to check whether your hepatitis B needs treatment in its own right.
- Daily PrEP as the preferred option if your hepatitis B does not need treatment, although event-based PrEP can also be offered.
- Clear advice about stopping, because of the risk of the hepatitis B flaring up.
Our chronic hepatitis B treatment guide explains when hepatitis B is treated and with what.
Why stopping can cause a flare
This is the most important safety point. If you have hepatitis B, the PrEP medicines are keeping the virus partly in check. Stop them suddenly, and the virus can rebound. The Truvada label carries a boxed warning: severe flares of hepatitis B, including liver failure, have been reported in people with hepatitis B who stopped Truvada2.
So, if you have hepatitis B:
- Never stop PrEP on your own. Plan it with your clinic.
- Expect follow-up tests after stopping. The Truvada label asks for close monitoring for at least several months2. The UK guideline recommends hepatitis B viral load and liver tests for 12 months after stopping, if you are not on other hepatitis B treatment1.
- Your clinic may suggest hepatitis B treatment instead of simply stopping, especially if you have significant liver disease2.
This also matters for the general rules on stopping PrEP described in our guide to starting, missing and stopping PrEP: those rules assume you do not have hepatitis B.
On-demand PrEP and hepatitis B
Event-based PrEP (such as the 2:1:1 pattern) means starting and stopping the medicine often. For people with hepatitis B, that pattern needs extra thought because of the flare risk described above. The UK guideline prefers daily PrEP for people with hepatitis B who are not on treatment, though it says event-based PrEP can also be offered1. Guidance differs between countries, so agree the plan with a clinic that knows your hepatitis B results.
Liver and other monitoring
Beyond the hepatitis B test at the start, people on PrEP have regular HIV tests, kidney tests, and screening for other sexually transmitted infections. The UK guideline also recommends hepatitis C testing for people at risk1. Our guide to PrEP side effects and tests sets out the routine schedule.
PrEP and hepatitis B treatment: same molecule, different job
- Hepatitis B treatment uses tenofovir (as TDF or TAF) or other antivirals to control a chronic hepatitis B infection, usually long term, with regular liver checks.
- PrEP uses tenofovir with emtricitabine to prevent HIV in people who do not have it.
The overlap is why your PrEP and hepatitis B care should be joined up. If you are prescribed tenofovir for hepatitis B and also need HIV prevention, tell both teams, so that one plan covers both.
Generic tenofovir medicines are listed on our tenofovir disoproxil fumarate and tenofovir alafenamide pages, with generic Viread and generic Vemlidy (for example Tafero 25 mg) for hepatitis B treatment.
Frequently asked questions
Does Truvada treat hepatitis B?
Its two ingredients are active against hepatitis B, but Truvada is approved for HIV treatment and PrEP, not for hepatitis B. Tenofovir alone, as Viread or Vemlidy, is the approved hepatitis B treatment.
Can I take PrEP if I have hepatitis B?
Yes, with specialist input. The UK guideline prefers daily PrEP for people with hepatitis B who are not on treatment, and your clinic will plan carefully how and when you stop.
Does PrEP protect against hepatitis B?
Do not rely on it. The UK guideline and the Truvada label both recommend hepatitis B vaccination for people who are not immune.
What happens if I stop PrEP and have hepatitis B?
The virus can flare up, sometimes severely. That is why stopping is planned with your clinic, followed by liver and hepatitis B tests for up to 12 months, or a switch to hepatitis B treatment.
Why was I tested for hepatitis B before PrEP?
Because PrEP medicines act on hepatitis B, your clinic needs to know whether you have it before you start, and to offer the vaccine if you are not immune.
Sources & references
- British Association for Sexual Health and HIV and British HIV Association. BASHH/BHIVA guidelines on the use of HIV pre-exposure prophylaxis (PrEP) 2025.
- US National Library of Medicine, DailyMed. Truvada prescribing information.
- US National Library of Medicine, DailyMed. Viread (tenofovir disoproxil fumarate) prescribing information.
- US National Library of Medicine, DailyMed. Vemlidy (tenofovir alafenamide) prescribing information.
Related reading
This content is for informational purposes only and is not medical advice. If you have hepatitis B, plan any change to PrEP or hepatitis B treatment with your clinic. Used as prescribed by a licensed medical professional.
Harsh Bootwala is a licensed clinical pharmacist with 12 years of experience. He holds a B.Pharm and M.Pharm from Bombay University. At OnlineMeds, he reviews medicine and health content to help ensure it is accurate, evidence-based, and easy to understand.