This page provides information about HIV prevention medicines, PEP and PrEP.



PEP stands for post exposure prophylaxis. It is sometimes called PEPSE. It is a combination of HIV medicines you can take after you have been exposed to the HIV virus to lower the risk of infection.

Taking PEP safely

PEP can be taken up to 72 hours after exposure although it is best to start within 24 hours. It must be taken exactly as instructed and for 28 days for it to work effectively. It may cause some mild side effects in the first few days, such as nausea, headaches or tiredness. Do not skip a dose or fail to complete the full month as this makes it less likely to work. Do not take recreational drugs while on PEP as there can be dangerous interactions.

Where to get PEP

You can get PEP from your local sexual health clinic. Out of hours you can go to your local emergency department, who will provide you with a five-day pack and then refer you to one of our clinics for further treatment and testing.


PrEP stands for pre exposure prophylaxis and is a combination of HIV medicines taken by HIV negative people before and after sex, reducing the risk of them getting HIV. Taking PrEP before being exposed to HIV means there’s enough medicine inside you to block the HIV virus if it gets into your body. 

Taking PrEP safely

PrEP can be used in two ways:

  • By regularly taking one tablet per day
  • Taking PrEP only when needed – this is known as 'event-based PrEP'. This involves taking two tablets 2-24 hours before sex, one tablet 24 hours after sex and a further tablet 48 hours after sex.

Both methods have been shown to be very effective when taken correctly. 

The drugs used in PrEP are the same drugs that are prescribed to thousands of people living with HIV every year. They are very safe and serious side effects are rare. As a precaution, people taking PrEP have regular kidney function tests.

PrEP is highly effective at preventing HIV, it will not protect you from other STIs or an unwanted pregnancy, and therefore we recommend practicing safe sex by using condoms or regular method of contraception. It’s important if you’re using PrEP that you go for regular STI screenings every three months.

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.

Who can take PrEP?

You can take PrEP if:

  • You're HIV negative
  • At high risk of HIV
  • Don’t always use condoms.

Factors related to a high risk of HIV include:

  • A recent STI (especially rectal infection or syphilis)
  • Recent need for PEP (post-exposure prophylaxis)
  • Using recreational drugs used for chemsex (crystal meth, mephedrone and GHB)
  • If your HIV positive partner isn’t currently taking their HIV meds regularly.

This helpful  guide to PrEP from i-base provides further information.

Where and how to get PrEP



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The Waldron Health Centre

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Trafalgar Clinic (Queen Elizabeth Hospital)

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