Q and A

Question

Is a negative HIV test four weeks after PEP okay?

Good day.

Is it possible to test positive after testing negative after completing 28 day of  PEP?

Answer

Hi

In the UK, people need to wait 4 to 6 weeks after the last dose of PEP before taking a 4th generation HIV antigen/antibody test.

If this test is negative after 6 weeks, then someone is told they do not have HIV. If it is negative after 4 weeks, it means HIV is unlikely, but that a second test should confirm this after a few more weeks.

There is no point taking an HIV test as soon as you finish PEP.

This is because the PEP could just be covering up or delaying a potential infection.

This answer was updated in June 2023 from a question first posted in November 2020. This is because UK guidelines now recommend testing after 6 weeks rather than after 4 weeks.

277 comments

  1. Tyrone

    Hi, I had unprotected sex with an HIV positive person on 3 August 2023 and subsequently started PEP within 72 hours. It’s been 4 weeks since I completed PEP, will a negative result using a nucleic acid test be conclusive?

  2. Josh Peasegood

    Hi Jasmine, please see here for more information: https://i-base.info/qa/factsheets/pep-faq

  3. Jasmine

    Hey I was with a girl 01 October at 2H00, we had protected sex with her, but the condom broke and I pulled out quickly and rush to the bathroom, urinate and wash off.
    I went quickly to buy test at pharmacy, I was negative and she was positive ! I went to clinic urgently at 9H, they gave me PEP for 28 days
    The first day I took PEP at 10H and I had bad side effects, and I took again at 20H, and since I took every day at 20H before sleeping for bad effects !
    I have 3 questions :
    – taking PEP night will work?
    – the doctor told me that PEP medicine it is the same with ARV, it is true ?
    – during my 28 days, can I transmit HIv to my wife ? And last why medicine for 28 days not 7 days

  4. Josh Peasegood

    Hi Seville, after 5 months your test result is conclusive. You do not have HIV and you do not need to take any more tests.

  5. Seville

    Hi I had sex with an hiv positive who later died of it. But after she was tested positive I went for my hiv test at 6weeks of exposure and it was negative. I was placed on pep for 28 days. 8 weeks after pep I went back for second test and I’m still negative but I’m feeling symptoms and I’m afraid. Should I consider the second result conclusive which was done after 5 months?

  6. Josh Peasegood

    Hi Samuel, as you have now tested positive after 2 months your result is conclusive. You do not have HIV.

  7. Samuel

    Hi doctor , was having sex with a positive lady and in the process the condom broke and I pulled out quickly and rush to the bathroom, urinate and wash off. But before the sex I was on prep but missed only two doses and before I started sex with her, I took one dose of prep and waited 3hours before sex and after sex I cont with my doses for extra 2months. Finally did hiv test during the prep course n still negative.. what are my chances of having turn positive

  8. Josh Peasegood

    Hi Granton, for more information about transmission please see here: https://i-base.info/qa/factsheets/hiv-transmission-and-testing

  9. Granton

    Hey,.. On 25th September night I slept with a girl and in the morning when we were testing she tested positive and me negative, 25th evening I was given prep and on 26th I went to public clinic and I was given pep, so I started pep after 45hours,…we had sex the whole night, long shots,… Am so scared, what’s the probability of me turning out negative? Thanks

  10. Josh Peasegood

    Hi John, you can confirm your status 6 weeks after the last dose of PEP. This will be done using a 4th generation antigen/antibody test. These are often used at health clinics.

    At home tests are 3rd generation and these will require 3 months after PEP to be conclusive.

    It is a good sign that you have already been testing negative. Have you been to speak with your doctor about your symptoms? These symptoms do not suggest HIV and side effects from PEP would only be present for the time you are taking the medication.

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