PEP (Pre-Expsoure Prophylaxis)

PEP – What is it?

PEP is a 28 day course of medication that if taken up to 72 hours after unprotected anal or vaginal sex will dramatically reduce your risk of contracting HIV. 

POST = After.

EXPOSURE = where someone may have had a person’s HIV an opportunity to enter their bloodstream, and therefore be at risk of contracting HIV.

PROPHYLAXIS = A treatment to stop an infection from happening. 

PEP – Getting it & Taking it

PEP must be taken within 72 hours of having unprotected anal or vaginal sex. The sooner you take it after the exposure, it better it works. 

PEP is ONLY available from GUM/STI clinics or A&E departments. We’d recommend you’d visit A&E as they’re walk-in and open 24/7. Whereas many GUM/STI clinics have limited opening hours and most require you book an appointment first. PEP is NOT available at GPs, pharmacies or at The Rainbow Project.

PEP is a 28 day course of medication. It is very important that you : 

  • Do not skip a dose or fail to complete the full month as this makes it less likely to work.
  • Do not double a dose if you miss one.
  • If you do miss a dose and you remember in less than 24 hours, take the next one as soon as you remember.
  • If you miss more than 48 hours of PEP it will be discontinued.
  • Do not take recreational drugs while on PEP as there can be dangerous interactions.
  • Tell your doctor about any other prescriptions/non-prescriptions/homeopathic remedies you are taking to ensure no there are no interactions with PEP.
  • Antacids (containing aluminium, magnesium or calcium), multivitamins and iron supplements should be avoided while on raltegravir once daily.

PEP can cause mild side effects such as nausea, tiredness and headaches. Most side effects will lessen as you continue taking your course of medication. Do not stop taking your PEP due to side effects without consulting a healthcare professional first. 

PEP – What happens next?

You will have to get tested for HIV to ensure you have not contracted it despite taking PEP. Usually the GUM/STI clinic will book you in for an STI screen three months and six months after your course has completed.  

You can book with ourselves a rapid HIV & syphilis test to know your status within ten minutes. You can get tested at least six weeks after the unprotected encounter, as this is when our tests can semi-accurately detect HIV. However, we’d always recommend you return for another test twelve weeks after the encounter, when our tests are their most accurate, to be certain of your status. To find out more about how to get tested visit click here.

Whilst you’re on PEP and awaiting an accurate negative/non-reactive HIV result you should practice safe sex with condoms and lube. You can order a free delivery of condoms & lube via post click here.

If you have unprotected anal or vaginal sex often then you might want to consider taking PrEP. A medication that you can take regularly to maximize your protection from HIV. For more information on PrEP click here. 


  • PEP must be taken within 72 hours, and sooner if possible!
  • Attend your nearest GUM/STI clini or Hospital A&E – don’t want until the clinic you prefer is open!
  • Practice safe sex til you get a negative/non-reactive HIV test.
  • Get tested 6-12 weeks after you had unprotected sex.

Share this page