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. It contains tenofovir alafenamide and emtricitabine, sometimes called ‘TAF PrEP’.

A long-acting injectable PrEP has been approved by the Food and Drug Administration (FDA) but it is not yet available in the UK.

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

Where to get PrEP


PrEP is now 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. 

Quote text

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

Taking PrEP


In clinical trials using PrEP tablets, PrEP has been used in two different ways:

  • taken regularly (one tablet per day). 
  • only taken when needed (two tablets two to 24 hours before sex, one tablet 24 hours later and a further tablet 48 hours after that). 

This second method is often called ‘on-demand’, ‘event-based’ or 2-1-1 dosing.

On-demand dosing has only been studied in gay and bisexual men.

Both methods have been shown to be very effective for anal sex and insertive vaginal sex. 

Daily dosing is recommended for women who need to take PrEP every day for seven days to be protected against HIV.

Daily PrEP is recommended for all trans people using hormone treatment as there isn’t sufficient data to support other dosing options.

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

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 support you to use the treatment safely and provide necessary tests.

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. As a precaution, people taking PrEP have regular kidney function tests.

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.

More information

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