PEP and PrEP

Read on for all of the information you need to know about the medications PEP and PrEP.

PEP (Post Exposure Prophylaxis)

If you think have been exposed to HIV in the last 72 hours (3 days), you should consider PEP, which stands for Post Exposure Prophylaxis.

PEP is a course of HIV medication that you can take if you have been at risk of HIV infection. You will have to take the medication for a month but if you start taking it within 72 hours of being at risk, it may prevent you from becoming infected with HIV.

PEP is a combination of drugs that should prevent HIV infection after a possible HIV exposure, if taken within 72 hours.

Post- After.

Exposure- A situation where HIV has a chance to get into someone’s body.

Prophylaxis- A combination of drugs that can stop infection happening.


The most important thing to remember is that HIV can be transmitted even if you have only had sex with an HIV positive person once. However, HIV is not transmitted every time an HIV positive person and an HIV negative person have sex.

The risk of transmission occurring depends on a number of factors:

  • The type of sex you have had.
  • Who you have had sex with.
  • The number of times you have been put at risk.

Lots of different things can make it more likely for HIV to be transmitted:

  • Having another sexually transmitted infection.
  • Bleeding during sex.
  • The HIV positive person being at the infectious stage of HIV.

This is when you have had sex that could cause you to come into contact with HIV. The most likely route of sexual transmission is vaginal or anal sex where a condom wasn’t used or a condom broke. You are less likely to transmit HIV through oral sex than unprotected vaginal or anal sex. Another way that HIV can be transmitted is sharing injecting equipment. If you are concerned about this you should speak to your doctor, nurse or other worker.


PEP can offer some protection, however it can’t be guaranteed that it will stop you from becoming HIV positive.


You will be given a course of anti HIV drugs. They work on different parts of the HIV virus to stop HIV multiplying and to help your immune system to fight off the possible infection.


  • Sexual health clinics. We recommend that you go to the sexual health clinic during their working hours. You do not need an appointment for this. Every hour counts, so they will try and see you as soon as possible.
  • Accident and Emergency department. If it is the evening or a weekend or you can’t go to your sexual health clinic, you should go to your nearest A&E department. The on call GU Medicine or Infectious Disease Registrar (and consultant if necessary) can be contacted via the hospital switchboard. Not all A&E departments will know about PEP, so you should take some information with you.
  • You can’t get PEP from your GP or any pharmacies.

PEP should be taken within 72 hours of possible HIV exposure. The sooner you start the more effective it is. You will need to complete the month long course of treatment unless your doctor advises you not to e.g if your sexual partner’s HIV status is known after HIV testing.


A health professional will see if it is suitable to prescribe you PEP by asking some questions about what you know about your sexual partner’s background and the type of sex you have had. They will then discuss the recommended course of action with you.


You might experience side effects such as feeling sick and/or diarrhoea. If you do have these, medication can be prescribed to minimise these side effects. Your blood will need to be monitored because in some cases PEP can affect your kidneys and/or liver. If you have any concerns about side effects, you can discuss this with your doctor, nurse or sexual health worker.


Many drugs can interact with PEP. This means that you need to tell the doctor who prescribes PEP about any over the counter prescriptions, alternative medication or recreational drugs that you are currently taking.


If you take PEP you will need some blood tests before you start the course, during treatment and afterwards:

  • Blood is taken straight away to check that you are not already HIV positive. Your doctor or nurse might talk to you about testing for other infections at this time.
  • Blood taken during the PEP course to check your body’s functions and to see if there are any issues.
  • Blood taken after the course of PEP to check that HIV infection has not developed.

A condom and water based lubricant, used properly, is the most effective way of preventing HIV transmission during sex. This includes making sure that the condom is on the penis before vaginal or anal sex occurs. We recommend that you have regular sexual health check-ups as not all sexually transmitted infections have symptoms but they can increase the risk of HIV transmission.


PrEP (Pre Exposure Prophylaxis)

Pre-exposure prophylaxis is a course of HIV drugs taken before sex to reduce the risk of getting HIV. It is taken as a tablet once a day and research suggests that if it is taken every day as directed, it is very effective in preventing HIV transmission.

PrEP is intended for people who are at high risk of getting HIV. This includes people with a partner who is HIV positive or those who have multiple sexual partners and find it hard to use condoms. This is different to post-exposure prophylaxis (PEP), which is taken after a potential exposure to HIV.

In the UK, PrEP is only available to people who have enrolled in a research trial. This means that PrEP isn’t currently available through the NHS on prescription. There is no agreement yet for when this might happen.

From August 2015, PrEP is being offered through a private service where a prescription may be purchased following an assessment.

PrEP Consultation Toolkit

For more information and guidance on the PrEP Public Consultation, see the resources below.

The PrEP Public Consultation asks for opinion on the policy specification on PrEP that was written by NHS England's Clinical Reference Group on HIV (and a sub-group specifically looking at PrEP). The deadline to submit a response is 23 September 2016. The full consultation, and the online survey to fill in, can be found here. If you are responding as an individual, please don’t be put off by the first page which asks for your Job Title and Organisation. You can still submit y our responses and leave these (or any of the question boxes) blank.

Toolkit for individuals

Toolkit for organisations

Other PrEP Resources

Buying PrEP online

Safe use and NHS monitoring
Find out more

The PROUD study, a PrEP clinical study in the UK

For more information, click here
Find out more

How does PrEP work and how does it impact on communities?

Click here to find out more
Find out more