Post-exposure prophylaxis (PEP) is a course of antiviral medication taken after a known or suspected exposure to HIV, in order to prevent infection. It is usually taken as one tablet daily, although in some circumstances a combination of two or three tablets a day may be prescribed.
When PEP may be needed#
PEP is intended for situations where you may have come into contact with HIV. Examples of a known or suspected exposure include:
- Condomless sex with a person whose HIV status you do not know, or who has HIV and is not on effective treatment
- A condom breaking or failing during sex
- Sharing needles or other injecting equipment
If the exposure was with a person who has HIV and a sustained undetectable viral load, PEP is not recommended, because there is no risk of transmission in that situation.
If you think you may have been exposed to HIV, do not wait for a routine appointment. A PEP provider will ask you a series of questions to assess your level of risk and decide whether PEP is appropriate for you.
Where to get PEP#
PEP can usually be accessed through:
- General practice clinics, including those that specialise in sexual health
- Sexual health clinics
- The emergency department of most public hospitals
If the exposure happens after hours, an emergency department is often the best place to start PEP as soon as possible, since timing is critical.
How to take PEP#
There are two things to remember about taking PEP:
- It must be started within 72 hours of the potential exposure
- It must be taken every day for the full 28-day course to work
Possible side effects#
PEP can cause side effects in some people. These may include:
- Nausea and vomiting
- Headaches
- An upset stomach or diarrhoea
- Fatigue or tiredness
If side effects are severe or troubling, talk to your prescriber.
Important things to know about PEP#
- It does not protect against other sexually transmissible infections (STIs) such as syphilis, gonorrhoea and chlamydia
- It is not a “morning-after pill” and is not the same as emergency contraception
- After taking PEP, it is a good idea to be tested for STIs and treated if necessary
Other ways to prevent HIV#
PEP is only one option. HIV transmission can also be reduced or prevented by:
- Using condoms, including internal (female) condoms, with water- or silicone-based lubricant during anal or vaginal sex
- Using clean, sterile injecting equipment and not sharing it
- Taking pre-exposure prophylaxis (PrEP) if you are at ongoing risk of HIV
- Achieving and maintaining an undetectable viral load (U=U) if you have HIV, by taking antiretroviral treatment (ART) as prescribed
The best approach depends on your risk factors and lifestyle. It helps to find the prevention method, or combination of methods, that works for you and your partners.
If you have used PEP more than once, it is worth talking to your doctor about PrEP. PrEP is a pill taken once a day and is highly effective at preventing HIV transmission when taken consistently as prescribed.
Key points#
- PEP is taken after a known or suspected exposure to HIV to prevent infection
- A PEP provider will ask you a series of questions to determine your risk and whether PEP is appropriate
- PEP can cause side effects in some people
- PEP must be started within 72 hours of potential exposure and taken every day for 28 days
- There are several effective ways to prevent HIV, including condoms, sterile injecting equipment, PrEP and U=U
Where to get help#
Sources & further reading
For evidence-based global guidance on this topic, consult authoritative public-health bodies such as the World Health Organization (WHO), CDC, NHS, and ECDC.