Can post-exposure prophylaxis (PEP) stop me getting HIV?

Post-exposure prophylaxis (PEP) may stop you developing an HIV infection if you’ve been exposed to the virus. However, it doesn’t always work.

You may have been exposed to HIV if you've: 

  • had unprotected sex (without using a condom)
  • had sex with someone with HIV and the condom broke
  • been injured with an HIV-infected needle

What is PEP?

PEP is a course of anti-HIV medication. You must start the treatment as soon as possible after you’ve been exposed to HIV, ideally within a few hours. The medicines must be taken every day for four weeks.

PEP is unlikely to work if it’s started after 72 hours (three days) and it won’t usually be prescribed after this time.

PEP makes infection with HIV less likely. However, it’s not a cure for HIV and it doesn’t work in all cases. Some strains of HIV aren't affected by the medicines.

Also, the treatment may not work if you:

  • take the medicines incorrectly
  • don't start taking the medicines soon enough

What are the side effects of PEP?

PEP can have severe side effects, such as:

If you’re already HIV-positive, but don’t know it, you could develop drug resistance to PEP if you don’t take your doses properly. This could limit your treatment options in the future.

Where can I get PEP?

PEP is only available on prescription. You can get PEP from:

However, PEP may not be available in all areas of England. GPs can't usually prescribe PEP.

Find your nearest GUM clinic 

Find your nearest A&E department

When you request to have PEP, you’ll be asked some questions, such as:

  • who you had sex with, to assess your risk of exposure to HIV
  • whether you had oral, vaginal or anal sex
  • whether the other person definitely had HIV  and if known, what was their "viral load"

PEP and HIV tests

You’ll be asked to take an HIV test before starting PEP treatment, to check whether you already have HIV. If you don’t agree to an HIV test, you won't be given PEP.

You’ll also need an HIV test after the treatment, to check that it’s been successful.

Safe sex

HIV can’t be cured. Don't rely on PEP to prevent HIV, because it doesn’t always work.

Using a condom is the best way to prevent the spread of sexually transmitted infections (STIs), including HIV.

Read the answers to more questions about sexual health.

Further information: