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Regimen. 1 tablet daily (can aslo be taken on-demand – see below)

Further actions. HIV & STI test every 3 months
+ Kidney function test every 12 months

Possible side effects. Nausea, headaches, bloating, diarrhoea, insomnia and feeling dizzy or weak may occur. See below for more information

Cost of treatment.

  • PrEP only: £35/month
  • PrEP 3 months supply plus HIV Test, Kidney Function Test, & urinalysis: £190

PrEP (Pre-Exposure Prophylaxis) is a HIV prevention strategy that involves taking medication on a regular basis to reduce the risk of acquiring HIV. There are two main recommended regimens:

1. Daily PrEP: This involves taking one pill every day, preferably around the same time each day. This regimen provides continuous protection against HIV and is considered highly effective when taken consistently.

2. On-Demand PrEP: This regimen involves taking two pills 2 to 24 hours before anticipated sexual activity, followed by one pill 24 hours after the initial dose and another pill 48 hours after the initial dose. This dosing strategy is only suitable anal sex. It is not suitable for vaginal sex.

Please note that the specific guidelines and recommendations for PrEP may vary over time, it is advisable to consult up-to-date information from reliable sources or clinicians in the UK.

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The Process

We will not administer PrEP 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

We will take a blood and urine sample in order to run the baseline tests before prescribing PrEP.

Administer PrEP

If it is still appropriate to proceed with PrEP (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 PrEP

What is PrEP and how does it work?

PrEP (Pre-Exposure Prophylaxis) is a medication used to prevent HIV transmission in HIV negative individuals.

To ensure effective protection against HIV, it is imperative that the medication maintains a steady and sufficient presence in the bloodstream. This is achieved through regular and timely dosing according to your clinician’s instructions.

When a person who is on PrEP is exposed to HIV through sexual contact or injection drug use, the antiretroviral drugs circulate in their system. These drugs create a barrier at the cellular level. They work by inhibiting an enzyme called reverse transcriptase, which is essential for the HIV virus to replicate itself.

By disrupting the function of reverse transcriptase, PrEP functions as a potent deterrent against HIV's ability to infiltrate and infect healthy immune cells. In essence, it effectively hinders the virus's capacity to initiate an infection within the body.

Where can I get PrEP?

You can access PrEP at Clarewell Clinics. Your clinician will be able to prescribe and dispense PrEP for you (at a cost of £35/month).

PrEP can also be prescribed through the NHS free of charge. PrEP is not available over the counter from your GP or pharmacy.

Why do I need a consultation before I am prescribed PrEP?

Before being prescribed PrEP (Pre-Exposure Prophylaxis), it is absolutely essential to have a thorough consultation with a healthcare professional.

PrEP medications are prescription-only and, while highly effective in reducing the risk of HIV infection when used correctly, they are not without potential side effects, some of which can be serious but are very rare. To ensure early detection of any adverse effects and to choose the right type of PrEP medication and regimen, a baseline assessment and follow-up plan, including appropriate blood and urine tests, must be established through consultation.

Furthermore, different individuals may require different combinations of PrEP drugs, such as Tenofovir disoproxil/Emtricitabine (Truvada) or Tenofovir alafenamide/Emtricitabine (Descovy), depending on their specific needs and health considerations. Additionally, proper adherence to the prescribed regimen is crucial for the effectiveness of PrEP.

A consultation can help individuals make informed decisions about the most suitable PrEP option, discuss potential side effects, manage the risks of other sexually transmitted infections, and understand the impact of PrEP on HIV testing accuracy. A consultation ensures that PrEP is used safely and effectively, enhancing sexual well-being and overall health.

If you are already taking or have taken PrEP, then a remote assessment and prescription may be possible, assuming you have no concerns or questions and that all required tests are up to date and do not need repeating.

How long does PrEP last?

One box of PrEP consists of 30 tablets.

How effective is PrEP at preventing HIV?

PrEP is very effective at preventing HIV. If taken as prescribed, it has about a 99% protection rate against HIV from sex.

However, PrEP’s effectiveness for preventing HIV transmission is limited. For individuals who risk being exposed to HIV through needle-sharing, it is essential to explore harm reduction strategies such as needle exchange programs. Using sterile needles, practicing safe injection techniques, and seeking support can help to reduce the risk of HIV transmission.

Is there anything I need to do or test for before taking PrEP?

Before taking PrEP, it is essential to have a HIV test to confirm your HIV-negative status. In cases where there may have been potential HIV exposure in the 45 days leading up to the initial test, an additional test is advised 45 days after this period to ensure your continued HIV-negative status. If you have experienced flu-like symptoms following a possible HIV exposure, you should not start PrEP until the necessary testing has been completed.

A urine dipstick test, which assesses protein levels in the urine, is always performed before prescribing PrEP medication. It is also recommended to undergo kidney function and Hepatitis B tests before initiating PrEP. This precaution is taken because a small percentage of individuals may experience kidney-related issues while on PrEP, and the presence of Hepatitis B can impact the specific approach to PrEP. Your clinician will thoroughly discuss this with you during your consultation.

How long does PrEP take to work?

You must take a daily dose of PrEP for seven days before you have unprotected sex. You must then continue with daily dosing for PrEP to remain effective in protecting you against HIV.

If you want to start taking daily PrEP but think you may have sex within the first 7 days, take 2 tablets at least 2 hours before you have sex. Then continue to take 1 tablet each day.

Are there any side effects to taking PEP?

Most patients taking PrEP experience no side effects. Occasionally, nausea, headaches, bloating, diarrhoea, insomnia and feeling dizzy or weak may occur.

Decrease in kidney function is rarely seen and tends to disappear after stopping PrEP medication. Mild thinning of the bone can sometimes occur but its clinical significance is not known.

If you are concerned about any side-effects before starting these medications, please discuss this with your clinician during your consultation.

Will PrEP protect me against other STIs?

No. PrEP only protects against HIV. You will still need to protect yourself against other STIs.

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

The most common reason for why PrEP may fail is if the medication is not taken as prescribed. Whilst missing one day or two days of daily PrEP does not necessarily mean you are not protected, it is very important to take PrEP as prescribed.

If you realise that you have forgotten to take a pill, then take it as soon as possible (within 12 hours) to maintain your protection. However, do not take a double dose to make up for a missed pill. If more than 12 hours have passed, consider it as a missed dose, skip it, and continue with the next scheduled dose at the usual time as part of your regular routine.

PrEP reaches maximum protection when taken daily for at least 7 days (for anal sex). If you are struggling to remember to take your pills on time, please contact your healthcare provider for support.

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 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.


Who can take PrEP?

Most adults above the age of 16 who are HIV negative can take PrEP. At Clarewell Clinics, we are only able to prescribe PrEP to patients above 18. PrEP is recommended for people who are at ongoing risk of acquiring HIV.

It is important to remember that PrEP is a preventative medication to be used before a possible exposure to HIV. PrEP can not be used to prevent HIV after a possible exposure. If you have had a possible exposure to HIV in the last 72 hours, you may be eligible to take PEP (Post-Exposure Prophylaxis). Ideally PEP should be taken as soon as possible, but definitely within 72 hours. Contact a sexual health clinic immediately or go to an emergency department (A&E) if you think you are in need of PEP.

Do I need to take PrEP?

You may benefit from taking PrEP if any of the following apply to you:

  • You have a HIV positive partner with an unknown or detectable viral load
  • You share needles, syringes or other injection equipment
  • You are considering getting pregnant and your partner is HIV positive
  • You engage in condomless sex
  • You engage in chemsex
  • You have partners from areas where there is high prevalence of HIV
  • You have previously been on PEP

Will my partner also need to be on PrEP?

Whether your partner needs to be on PrEP depends on various factors, including both partners' HIV status, the type of sexual activity you engage in, and your overall risk factors. Here are some general guidelines:

1. If one partner is HIV-positive and the other is HIV-negative (a serodiscordant relationship), the HIV-negative partner can take PrEP to reduce their risk of contracting HIV, although this is not needed if the HIV positive partner is on treatment and has an undetectable viral load.

Undetectable = Untransmittable (U=U).

2. If both partners are HIV-negative and in a mutually monogamous relationship then PrEP is not needed.

3. If either partner is involved in open relationships or has multiple sexual partners, considering PrEP is advisable.

4. If both partners share risk factors, such as injection drug use, it might be beneficial for both partners to be on PrEP.

What health conditions may stop me from being eligible for PrEP?

You may not be eligible for PrEP if:

  • You are HIV positive
  • You have a weakened immune system
  • You have liver or kidney problems
  • You have had an allergic reaction to tenofovir disoproxil, emtricitabine or any other PrEP medication

Please let your clinician know if any of these conditions apply to you. It is also important to let your clinician know if you have Hepatitis B as this could affect how you need to take PrEP.

Advice on taking PrEP

What is event based dosing?

On-demand, or event-based dosing, is a viable option for those who are giving and/or receiving anal sex. This way of dosing is suitable if you are only having sex once per week or if you are having sex several times over a few days per week.

On-Demand dosing involves:

  • Taking a double dose of PrEP (two pills) 2-24 hours before you have sex
  • Taking a single pill 24 hours after the double dose
  • Taking another single pill 24 hours after that

If you are having sex over a few days, keep taking the pill every 24 hours until you have had two sex-free days.

Event-Based Dosing is not an option if you have Hepatitis B, as it might cause liver inflammation.

How long can I stay on PrEP?

There is no limit to how long you can stay on PrEP, even if you are currently not sexually active. However, if you plan on using PrEP long-term, it is important to undergo regular HIV tests every 3 months, urine tests every 3 months and kidney function tests every 12 months.

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

If you realise that you have forgotten to take your PrEP dose, then take it as soon as possible (within 12 hours) to maintain your protection. However, do not take a double dose to make up for a missed pill.

If more than 12 hours have passed, consider it as a missed dose, skip it, and continue with the next scheduled dose at the usual time as part of your regular routine.

How can I stop taking PrEP? Can I stop taking PrEP half way through?

As you go through life, your situation may change and you may not always need to take PrEP. If you have not recently had any possible exposure you can stop taking the PrEP medication right away.

However, if you are a cis man and have recently had a sexual encounter that could have exposed you to HIV, you must take two more daily doses before you can stop taking the medication.

For all other instances, you must keep taking seven daily doses after the last possible exposure before you can safely stop taking the medication.

What happens if I vomit after taking my dose of PrEP?

If you vomit less than an hour after taking your dose of PrEP, take another tablet. Vomiting shortly after taking the medication may mean that the body did not fully absorb the drug, and taking another tablet helps ensure the intended dose is ingested.

Can I drink alcohol when taking PrEP?

PrEP is not negatively affected by drinking alcohol.

Can I take PrEP when I am on contraception or going through hormone treatment?

PrEP will not affect your contraception or hormone treatment.

Testing after PrEP

Do I need a follow up appointment after finishing my course of PrEP?

PrEP (Pre-Exposure Prophylaxis) is an ongoing medication unlike PEP (Post-Exposure Prophylaxis). It is recommended to come in for follow-up tests, check ups and repeat prescriptions every three months while you are on PrEP.

Will I need regular testing if I am on PrEP?

Once you have started your PrEP medication, you will need to have:

  • A HIV blood test every 3 months
  • A urine test to rule out any abnormalities in the kidneys every 3 months
  • An STI screen (if there is a risk of getting infection) every 3 months
  • A blood test to rule out any abnormality in the kidney function (every 12 months)

It is recommended that you have a kidney function test once per year, although some people may require more regular kidney function monitoring.

Will taking PrEP affect my HIV test results?

PrEP (Pre-exposure Prophylaxis) and PEP (Post-exposure Prophylaxis) medications are known to interfere with the performance and interpretation of the 4th generation HIV test results by altering the amount of virus in the blood, and potentially delaying the development of antibodies.

Furthermore, these medications will particularly affect the level of p24 antigen, causing it to either appear for a shorter period of time at a smaller level, or not appear at all.

If you are currently taking PrEP or PEP, you should take the 4th generation HIV test 45 days after completing your course of medications for a reliable and conclusive HIV result.

Can taking PrEP affect the accuracy of other STI results?

It is highly unlikely that PrEP would affect the accuracy of other STI results.


Sexual Health Consultation £60

PrEP only £35/month

PrEP 3 months supply plus HIV Test, Kidney Function Test, & urinalysis £190

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.