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Pre-exposure Prophylaxis (PrEP)

PrEP (pre-exposure prophylaxis) is a drug taken by HIV-negative people before and after sex that reduces the risk of getting HIV. It works for everyone however you identify, and also when you are taking the contraceptive pill or gender confirming hormones.

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 – before it has the chance to infect you.

Taking PrEP

For women and trans people using PrEP the recommended dosing regimen is to take one tablet per day. This keeps the amount of drug in the body at a level to provide protection against HIV.

For men there are a variety of dosing options:

  • Taking one pill a day.
  • Taking PrEP when needed, also known as ‘on demand dosing’ – taking two tablets two to twenty four hours before sex, one tablet twenty four hours after sex, and one tablet forty eight hours after sex, a total of four tablets.
  • T’s and S’s – as you don’t always know when you’re going to have sex, it may be easier to take the pills on the same days every week – the T’s are Tuesday and Thursday and the S’s are Saturday and Sunday. 

For men, taking four pills a week still provides the levels of the drug needed in the body to protect against HIV.

Taking PrEP safely

If you’re getting PrEP from outside the NHS, it’s important that you talk to an adviser from a sexual health clinic before you start taking the pills. They will support you to use the treatment safely and provide necessary tests, like HIV and kidney function tests.

In most large studies no one has become infected if they took PrEP as recommended. However, if you don’t follow the correct dosing regimen it may not work.

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

A few people experience nausea, headaches or tiredness and, very rarely, the medication can affect kidney function. As a precaution, people taking PrEP have regular kidney function tests.

Although PrEP is highly effective at preventing HIV, it doesn’t provide protection 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.

Where to get PrEP

PrEP is available for people who are at risk of getting HIV from sexual health clinics across the UK. You should check with your local service to find out which clinics are providing PrEP.

If you’re thinking about getting PrEP from outside the NHS there are a number of things to consider, you can find more information from I Want PrEP Now.

Is PrEP right for me?

Answer some short questions and based on your answers we'll recommend whether PrEP is right for you.

Commonly Asked Questions

Experts answer your questions on HIV, STIs and sexual health.