Person holding a blue pill in their hand and a glass of water.

How PrEP works

Taking PrEP before being exposed to HIV means there’s enough drug inside you to block HIV if it gets into your body. The medication most commonly used for PrEP is a tablet which contains tenofovir disoproxil and emtricitabine (drugs commonly used to treat HIV). It is sometimes called Truvada but most of the PrEP we use in the UK is generic PrEP.

A second pill has been approved for use as PrEP – the branded drug Descovy or its generic equivalent, which is now available on the NHS. It contains tenofovir alafenamide and emtricitabine, sometimes called ‘TAF PrEP’.

Unless you have ongoing kidney issues, osteoporosis or are under 18 you will be prescribed Truvada (the generic version of the drug). Descovy isn’t prescribed for anyone born female as currently there is no research to show it works at prevention HIV taking hold in their body.

A long-acting injectable PrEP has been approved by the Food and Drug Administration (FDA) but it is not yet available in the UK. In February 2025 the Scottish Medicines Consortium approved cabotegravir (CAB-LA) for NHS use in Scotland. For those who face challenges with daily PrEP pills, a long-acting injectable option could be life-changing.

PrEP vaginal rings are used in some parts of the world but are not available in the UK.

Where to get PrEP

PrEP is available free on the NHS in England from sexual health clinics.

In Scotland, PrEP is available through sexual health clinics. Visit the PrEPScot website to find out more information about how to access it.

In Wales, PrEP is available through sexual health clinics. For more information, see the Public Health Wales website.

All GUM clinics in Northern Ireland offer initial consultation and assessment appointments for centrally dispensed PrEP. 

Taking PrEP has enabled me to trust again, have relationships and build bridges.

Harry Dodd
PrEP user

Taking PrEP

Most people take PrEP every day, but you can take 4 pills a week and still be protected against HIV. Some people take PrEP just before and after sex.

Before taking PrEP you should take an HIV test to confirm that you are HIV negative.

PrEP can be taken in different ways to protect against HIV:

  • Daily: taking one pill a day, starting with a double dose.
  • Four pills a week: taking four pills a week consistently.
  • On-demand/ event-based: taking PrEP only around the time you have sex. Pills are taken a few hours before sex and for up to seven days after. 

On-demand/ event-based PrEP has different dosing recommendations depending on the type of sex you are having:

  • Receptive anal and insertive vaginal/neovaginal or anal sex: PrEP started with a double dose (two pills) 2-24 hours before sex, one tablet 24 hours later and a further tablet 48 hours after that. 
  • Receptive vaginal/neovaginal sex: PrEP started with a double dose (two pills) 2-24 hours before sex, one tablet daily for seven days after.

The same dosing recommendations apply for all trans and non-binary people using gender-affirming hormone treatment.

Read more about using PrEP as a trans masculine person and using PrEP as a trans feminine person.

PrEP can also be used to prevent HIV if used just before and after injecting recreational drugs.

Taking PrEP safely

If you’re thinking about getting PrEP from outside the NHS, it’s important that you talk to an adviser from a sexual health clinic. They will be able to advise you on taking PrEP safely, and help you get your tests for HIV and other sexually transmitted infections (STIs). They can also do a blood test to check your kidney function.

The drugs used in PrEP are the same drugs that are prescribed to thousands of people living with HIV every year. They’re well tolerated and serious side effects are very rare. 

When starting PrEP, some people experience nausea, headaches or tiredness but these symptoms usually pass within a week. Very rarely, the medication can affect kidney function. 

PrEP is highly effective at preventing HIV. Condoms can help protect you from other STIs or an unplanned pregnancy.

It’s important if you’re using PrEP that you go for regular STI screenings every three months. You should also take HIV tests every three to six months however you get your PrEP.

More information

If you like to speak to someone about PrEP, call THT Direct on 0808 802 1221.