Q and A


Does PEP have side effects?


I am confused with PEP treatment, specifically about the side effects.

From sexual health charities I hear that PEP treatment can cause occasional side effects which may or may not go over the 28 days treatment. Another one (THT) says that the side effects are extreme and about 1 in 5 people on PEP stop taking it as a result.

The sexual health nurse said that side effects on PEP are very common and are severe.

I’ve heard from 3 people who have had PEP and they said that they didn’t get any side effects.

What’s the official line on PEP and side effects? I thought that PEP usually uses recommended triple therapy, using drugs that are well tolerated. Is the conflicting information I am receiving due to outdated data or current data?

Thank you for any clarity you provide.


All meds have some risk of side effects, but for PEP this risk is usually low. If side effects do occur, they are usually mild.

This depends on the meds used in the PEP combination.

In the UK in 2018, the PEP combination is usually raltegravir plus a combined pill with tenofovir DF/emtricitabine, which generally causes very few side effects, if any.

Even general side effects like nausea, diarrhoea and tiredness are not experienced by most people.

If mild side effects occur, they usually get easier after the first week or two as your body adjusts.

PEP that contains a drug called efavirenz is not recommended in the UK, though is used in some countries where there is less choice for HIV drugs. Efavirenz has a higher risk of side effects including mood changes and vivid dreams.

Discontinuation rates for PEP are often not very good. Studies of health workers who are exposed with a needle-stick injury report many people stop before the full month of treatment.

Note: This answer was updated in February 2018 from a question first posted online in June 2009.


  1. Roy Trevelion

    Hi Jean,

    Sorry if I caused confusion. I meant to point out that a tiny number of people take up to 3 months to produce antibodies to HIV. I didn’t mean that the tests cannot detect the antibodies, just that they’ve not yet been produced.

    But you reported flu like symptoms whch are similar to seroconversion. But if you keep testing negative perhaps you could talk to the doctor about the symptoms.

  2. Jean

    thx for your reply
    but i have confusion should test again??
    it been 4 month after exposure and 3 month after course of pep.
    i test today it is negative.
    you mean that rapid test can not detect hiv in 3 month???

  3. Roy Trevelion

    Hi Jean,

    It’s great you took PEP for the full month.

    However, HIV antibody tests, like the rapid test, do not work as soon as you are infected. This is because it usually takes several weeks to generate antibodies to HIV.

    This is called the ‘window period’. Most people generate this response within 4–6 weeks, but approximately 5% of people take up to 3 months. Very rarely it can take longer.

    The window period of 3 months should begin after you finish PEP.

    Please see more info here on this Q&A.

  4. Jean

    i paid sex from 19/10/2018 with someone who has hiv status. i took pep full months.
    i test many time with rapid test i always test negative but i have more rash, flu like, nodes, headache,night sweat.
    i test negative again today with rapid test again.
    1.Should i beleive rapid test can detect well an hiv???
    2.Should i feel free?
    3.should test again??

    Thank you!!!!


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