PrEP stands for pre-exposure HIV prophylaxis. It’s a way of preventing HIV infection by taking a pill on an ongoing basis before sex. It’s taken by someone who doesn’t have HIV, to prevent them from getting HIV. The PrEP pill is an antiretroviral drug – the same type of pill taken by someone who already has HIV to treat HIV.
PrEP is most commonly taken as a once-a-day pill of a drug called Truvada (a combination of tenofovir and emtricitabine). Truvada is one of the drugs commonly taken by someone with HIV as an HIV treatment. Trials have shown that PrEP works best when it is taken regularly – this ensures that levels of drug in the blood are high enough to be protective against HIV.
Recent trials have also explored if oral PrEP might work if taken less regularly, particularly before and soon after sex. This way of taking PrEP might be more popular for people who know in advance when they are going to have sex. Many HIV researchers think there are still questions to be answered about taking PrEP on a non-daily basis. Click here for more information on daily and non-daily use of PrEP.
If a person taking PrEP is exposed to HIV, the PrEP drugs they have taken prevents HIV from entering their cells and from replicating. This stops HIV from establishing itself and stops the person taking PrEP from becoming infected with HIV.
Research shows that PrEP needs to be taken daily for between 4 and 7 days for protective levels to be reached in the blood and the rectum. It takes longer for protective levels to be reached in the vagina and cervix – so people with a vagina or a cervix may need to take PrEP on a daily basis for three weeks before it becomes effective.
The short answer is yes. Studies across the world have shown that daily oral PrEP is highly effective. The iPREX trial showed that it was most effective when taken every day. Aidsmap’s briefing paper provides an excellent overview of PrEP research.
Most people who take PrEP don’t experience side effects. When people do get them they tend to go away on their own within a few weeks. Side effects can include stomach problems, headaches or tiredness. In the PROUD study participants reported few side effects, and almost everyone who stopped PrEP because of side effects were able to start PrEP again.
PrEP is different from PEP. PEP is taken for up to 28 days after someone has had sex if they think they’ve been exposed to HIV. The main difference between PEP (post– exposure prophylaxis) and PrEP (pre-exposure prophylaxis) is that PEP is taken after sex, if someone thinks they’ve been exposed to HIV, and PrEP is taken on an ongoing basis before sex. More information about PEP is available here.
At the moment PrEP is only available for free for people enrolled on the PROUD clinical trial. It is not currently available on the NHS. Some people have started to buy PrEP though private prescriptions – but this is expensive. Others have started to buy PrEP online from overseas. If you’re considering doing this, it’s important to be aware of some key information.
If you are considering starting PrEP, it is highly recommended that you discuss this with a doctor at a sexual health clinic. Medical staff will be able to help you decide if PrEP is right for you, and will be able to offer important tests before starting PrEP – such as kidney function tests. Most importantly, they will be able to provide the right kind of HIV test – PrEP should only be started if you know you are HIV negative for sure.
If PrEP becomes available on the NHS, it is likely to be mainly available from sexual health clinics. They will be guidelines about who will be able to receive it – such as individuals who are at greater risk of getting HIV. It will not be recommended for everyone.
In March 2016 NHS England released a statement on provision of PrEP in England that said that Local Authorities and not NHS England are responsible for funding PrEP. This was despite NHS England starting a formal process 18 months ago to decide if NHS should fund PrEP.
NHS England is making available £2m over 2 years to run pilots to 500 men at risk of HIV infection. It is not yet known where the sites will be based. There is currently no plan to make PrEP more widely available on the NHS.
In February 2016 the PROUD study announced that it would continue to provide PrEP beyond June 2016. The March 2016 NHS England statement made a commitment of further support to PROUD participants. People on PROUD are encouraged to contact their trial clinics and discuss their options.
In Scotland, PrEP is now available for free on the Scottish health service for people 16 and over who live in Scotland. Find out more here.

Please note, this information is correct and accurate at the time of posting. Things can change quickly and we will do our best to keep things updated, however please confirm facts for yourself before making decisions based on this information.
Thank you to Prepster for providing this information.