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HIV PEP (Post-Exposure Prophylaxis)

Method of prevention. Oral anti-retroviral medications

Length of medications. 28 days course

Further actions. HIV 4th gen test at 45 days+ 90 days after exposure

Possible side effects. Nausea, lethargy, dizziness, loss of appetite, trouble sleeping, headache, and stomach-ache.

Cost of treatment. £550 (Assessment, PEP medications for 28 days, and baseline blood and urine tests).

Post-exposure Prophylaxis (PEP), or Post-exposure Prophylaxis after sexual exposure (PEPSE), is a course of medications that significantly reduces the risk of developing a HIV infection when taken as prescribed.

PEP medication should be taken daily for a duration of 28 days after the initial dose. While PEP can cause side effects such as nausea and diarrhoea, it should not lead to any significant complications.

If you believe you have been exposed to HIV, it is essential to seek immediate medical attention by visiting A&E or a sexual health clinic in order to evaluate your situation and determine if PEP is appropriate for you.

It is crucial to initiate PEP within 72 hours after a potential HIV exposure. Once the 72-hour window has passed, PEP is no longer effective and therefore not recommended. Every hour counts.

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The Process

We will not administer PEP without first discussing it with you.


In order to be most prepared and leave plenty of time for questions & discussions, we will ask you to fill out a simple questionnaire.


We will begin by assessing your medical & sexual history, any symptoms you may be experiencing and discuss any questions you may have.

Sample collection

If we believe you are eligible for PEP, we will take a small blood sample and urine sample in order to run the baseline tests.

Administer PEP

If it is still appropriate to proceed with PEP (and you would like to), we will administer the medications.

We follow guidelines set by

Medicine is a complicated subject and sometimes these guidelines don’t always hold the answers.

For example, treating an STI in a patient who has developed a resistance to routinely used antibiotics.

Unlike most private clinics, we have medical consultants here to help you navigate through such problems and get you on the right track in no time.

Frequently Asked Questions

About PEP

What is PEP and how does it work?

Post-exposure Prophylaxis (PEP) or Post-exposure Prophylaxis after sexual exposure (PEPSE), is a medication regimen used to prevent a HIV infection after a possible exposure.

When taken as prescribed, PEP medication helps to block key steps in the HIV replication cycle, preventing the virus from multiplying and spreading throughout the body. By inhibiting viral replication, PEP reduces the viral load and the likelihood of establishing a persistent infection.

It is important to start PEP within 72 hours (ideally within 24 hours) after being exposed to HIV. The sooner you begin PEP, the more effective it is likely to be.

PEP is not recommended to replace other HIV protective measures or medication and should only be given in an emergency. You should not rely solely on PEP to protect you from HIV.

If you are likely to be at further risk of HIV transmission, and your HIV test is negative after completing your course of PEP, you may wish to consider taking PrEP.

Where can I get PEP?

We are able to provide PEP at short notice.

You can also access PEP through your local sexual health clinics, or through the NHS. If you need PEP during late hours, you must go to A&E as soon as possible.

What will happen during my consultation?

During the consultation, your clinician will assess your risk for HIV, your eligibility for PEP, and run baseline blood and urine tests to see if it is safe for you to have PEP.

Your clinician will also discuss your medical history, the medications that may be prescribed, any possible side-effects, follow-up testing, and safer sex practices.

What medications does PEP consist of?

PEP is made up of two medications known as:

1. Truvada (taken once daily for 28 days)

  • Called ‘PrEP’ (Pre-Exposure Prophylaxis) when taken without Raltegravir
  • Combination of Tenofovir and Emtricitabine (FTC)

2. Raltegravir (taken twice daily for 28 days)

In some circumstances other combinations of HIV drugs may need to be used when there is concern about potential side effects or resistance of the virus in the source person.

Is generic PEP any less effective?

As long as the medications are genuine, generic drugs are expected to be just as effective as branded PEP.

Generic HIV medications are used widely in treatment of HIV positive patients throughout the world and no concerns have been reported of inferior results from generic drugs compared to branded ones.

Are there any side effects to taking PEP?

PEP is a very safe medication, however, common side-effects include nausea, lethargy, dizziness, loss of appetite, trouble sleeping, headache, and stomach-ache.

Symptoms of an allergic reaction to PEP include a skin rash or a flu-like illness. However, this can also be a sign of a HIV infection.

If you develop a skin rash or a flu-like illness while taking PEP, or in the 12 weeks after stopping PEP, you should contact your clinician as soon as possible.

Will taking PEP protect me against other STI's?

PEP is only effective in preventing a possible HIV infection after being exposed. Taking PEP will not protect you from other STI’s.

What are the common reasons why PEP may fail to prevent HIV infection, and how can these be mitigated?

PEP may fail, or be less effective if:

  • You miss a dose or fail to complete the full month of PEP.
  • You miss more than 48 hours of PEP.

If you do miss a dose and you remember in less than 24 hours, take the missed dose as soon as possible. Do not double the dose.

  • A few ways to ensure you have taken your PEP medication correctly are:
  • Investing in a pill box and keeping it near to you.
    Scheduling reminders on your phone on when to take your medication.
  • Place your medication somewhere you will see it, assuming it is safe to do so and out of reach of children. Keeping it next to your toothbrush, for example.
  • Note down when you have taken a dose of your medication so that you do not mistakenly double up on doses.

If you are confused or concerned about your PEP dose, please contact your clinician as soon as possible.

Can I have sex while taking PEP?

Ideally, you should wait until you have finished taking PEP and have received a negative HIV result before having sex again.

However, if you cannot wait it is important to be consistent and reliable with condom use to avoid putting others at risk.


Who can take PEP?

PEP can be prescribed for those who are HIV-negative and in the last 72 hours may have:

  • Had unprotected receptive or insertive anal sex with someone who is at an increased risk of having HIV or is HIV-positive with a detectable viral load.
  • Had unprotected receptive or insertive vaginal sex with someone who is at an increased risk of having HIV or is HIV-positive with a detectable viral load.
  • Shared needles
  • Been sexually assaulted
  • Been exposed to HIV-contaminated blood due to a needle-stick injury or other occupational accidents
  • Have been taking PrEP but have missed a dose before an episode of unprotected sex with someone who is at an increased risk of having HIV

Will my partner need to be on PEP?

If you have had sex with your partner in the last 72 hours since being exposed to HIV, your partner may be eligible for PEP.

It is important to remember that PEP is only given in an emergency.

If your partner is regularly exposed to HIV through high-risk behaviours, it may be beneficial for them to be on PrEP instead. However, it is your partner’s decision whether to begin PrEP.

Will I need to be on PEP if my partner is HIV-positive?

If you have been recently exposed to HIV (in the last 72 hours) from a partner who is HIV-positive and not effectively managing the virus, it is essential to try and access PEP as soon as possible.

However, if your partner’s viral load is undetectable and they are managing their HIV treatment according to the instructions laid out by their clinician, it will not possible for HIV to be transmitted. Please note that until your partner's viral load is considered undetectable = untransmittable (U=U), it is still possible for HIV to be transmitted.

PEP is not a guarantee against HIV transmission and it should not replace consistent and correct use of other HIV preventative measures, such as PrEP and condoms.

Are there any health conditions that can stop me from being eligible for PEP?

PEP is only indicated for those without a HIV infection. If you are already HIV-positive, you will not be eligible for PEP.

The dose of PEP must be adjusted to avoid any adverse side effects in those with compromised renal (kidney) function, specifically with a creatinine clearance (a measure of kidney function) below 50mL/min.

PEP can be considered at any time during pregnancy (despite the risk to the pregnant person and the foetus) due to the increased risk of sexual HIV acquisition during pregnancy. Patients should be made aware that the use of PEP during pregnancy is unlicensed and that their risk and benefits must be properly assessed before PEP can be administered.

Advice on taking PEP

What happens if I miss a dose of PEP or take it late?

The effectiveness of PEP in reducing the risk of HIV infection relies on consistently taking the prescribed medications according to the recommended schedule.

If you miss a dose of PEP:

1. Take the missed dose as soon as you remember. If it is time for your next dose, skip the missed dose and resume your regular dosing schedule.

2. Do not double the dose to make up for the missed one. Taking two doses together can increase the risk of side effects without providing any additional benefit.

3. If you are unsure about what to do or if you have missed multiple doses, contact your clinician.

It is essential to adhere to the prescribed dosing schedule as closely as possible. If you have any concerns or questions about your PEP regimen, you should consult your clinician.

Can I just take 7 days worth of PEP?

PEP must be taken for 28 days. At times, you may be given a 5 day course by sexual health clinics, or A&E, to initiate PEP. However, the remaining 23 doses will need to be taken. You can access the other 23 doses by visiting a sexual health clinic.

Can I stop taking PEP half way through?

It is recommended to finish your full course of PEP. Stopping PEP half-way through the course will reduce its effectiveness at preventing HIV.

Can I drink alcohol while on PEP?

Alcohol does not affect how effective PEP is, however, if you drink too much alcohol you may forget to take your daily PEP dose on time and this can cause the PEP to be less effective.

Can I take PEP with other medications?

Although PEP medications are generally safe, they may interact with other medications. It is important to be honest with your clinician about any medications you are currently taking so that they can ensure there are no drug interactions.

Testing after PEP

Do I need a follow up HIV test after finishing my PEP course?

While PEP significantly reduces the risk of acquiring HIV, it is not 100% effective. Therefore, to confirm whether PEP has been effective at preventing a HIV infection, a 4th generation HIV test should be taken 45 days after you have taken your last dose of PEP.

You can opt for a HIV-1 RNA PCR test for the early detection and intervention of HIV. However, this will have to be followed by a 4th Generation HIV test at 45 and/or 90 days after your last dose of PEP.

Will taking PEP affect my HIV-1 RNA PCR test results?

The antiretroviral medications used for PEP may suppress viral replication and lower the amount of HIV RNA in the bloodstream. If you have tested for HIV too soon after finishing PEP, the HIV-1 RNA PCR test may yield false-negative results.

Your clinician will advise on the timing of testing to ensure accurate results.

Can taking PEP affect the accuracy of other STI results?

Taking PEP will significantly affect the accuracy of any HIV test results that you receive during your treatment plan. However, PEP should not affect the accuracy of other STI results.

PEP does not interfere with the accuracy of tests for Chlamydia or Gonorrhea. The standard diagnostic tests for these infections, such as nucleic acid amplification tests (NAATs), are not affected by PEP medications.

PEP should not affect the accuracy of syphilis testing. The tests used to diagnose syphilis detect antibodies produced by the body in response to the Syphilis bacterium. PEP medications do not typically interfere with the production of these antibodies or affect the accuracy of syphilis antibody tests.

PEP does not have a significant impact on the accuracy of Hepatitis B or Hepatitis C testing. The standard blood tests used to diagnose these viral infections detect specific markers or antibodies associated with the viruses. PEP medications do not interfere with the detection of these markers.

PEP does not affect the accuracy of herpes testing either. Herpes is typically diagnosed by specific tests that detect the presence of herpes simplex virus (HSV) DNA or antibodies. PEP medications do not interfere with the detection of HSV DNA or the production of herpes antibodies.


Sexual Health Consultation £60

PEP (Assessment, PEP medications for 28 days, and baseline blood and urine tests) £550

4th Generation HIV Test (with Drop & Go) £70

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Next Steps 

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Reviewed by: Aaron Williams
Written By: Shannon Abraham

Last reviewed date: 17 October 2023
Next review due: 17 October 2026

Whilst this content is written and reviewed by sexual health specialists, it is for general guidance only. It is not intended to replace the advice of your clinician.