HIV PREVENTION

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How and when to take PrEP

Pre-exposure prophylaxis (PrEP) is prescription medication used by HIV-negative individuals to reduce their chances of acquiring HIV. It is important to get tested for HIV before you begin PrEP to ensure you are HIV-negative. This is because taking PrEP while living with HIV can lead to drug resistance, making it more difficult to treat HIV.1

There are different ways to take PrEP, so you should speak to your doctor about which method suits your needs best.1

How to take PrEP

For PrEP to be highly effective at preventing HIV it needs to be taken as advised by a healthcare professional to maintain sufficient drug levels in the body.2

PrEP is available in two forms: as tablets and as long-acting injectables and how you take it depends on which form you are prescribed.2,3 Furthermore, if you are prescribed PrEP in tablet form, there are two ways to take it: daily or on-demand.4

Daily oral PrEP

Daily PrEP is for people who have anal and vaginal/frontal sex as well as people who inject drugs.1,4 When on daily PrEP, you should take one tablet every day, ideally at the same time each day.4

It is important to remember that you would need to take your daily PrEP pills for seven consecutive days before you have sex to ensure you are fully protected. However, if you are just starting daily PrEP but wish to engage in sex before seven days then you can start PrEP with two tablets 2–24 hours before sex and then one tablet daily following that.4

On-demand PrEP

On-demand PrEP is for people who have anal sex and is not currently recommended for people who have vaginal/frontal sex or people who inject drugs.1,4 Here are the steps to properly take PrEP on-demand:4

  • Take two tablets (double dose) 2–24 hours before anal sex.
  • Take one tablet 24 hours after the double dose.
  • Take another tablet 48 hours after the double dose.

If you plan to have sex more than once, you should continue taking one tablet every 24 hours for the days you have sex and then one tablet every day for the next 2 days after last having sex.4

This way of taking PrEP is also sometimes referred to as “2:1:1” or episodic dosing.1,2

Long-acting injectable PrEP

Long-acting injectable PrEP is for people who have anal and vaginal/frontal sex as well as people who inject drugs.1 Long-acting PrEP is an injection from your doctor several times a year. The location of the injection varies depending on the kind of long-acting PrEP you are prescribed.5–7 You may also need to take oral tablets first to check for any side effects before beginning injections, however, this step is optional.5–7

Some people may prefer long-acting injectable PrEP including those who have difficulty adhering to a daily oral PrEP regimen or prefer a more discreet method of PrEP due to HIV stigma.1,8,9

What to do If you mIss a PrEP dose

It is important to take your PrEP medication exactly as prescribed because this is when it is most effective.1,3 If you are regularly missing doses you should speak to your healthcare provider about different options for PrEP as there may be something else that would suit your needs better. 

However, missing an occasional PrEP dose does not mean you are no longer protected from HIV.1,4 Depending on how you are taking PrEP there are different ways to approach missing a dose. 

Missed daily oral PrEP

If you miss a dose of daily PrEP, you can still take it within 12 hours of the missed dose. If it is any later, then wait and take your next dose at the usual time.4 With daily PrEP, you can still have full protection as long as you take at least six doses in a week.4

If you miss more than two doses of daily PrEP, you should contact your healthcare provider for advice.4

Missed on-demand PrEP

A missed dose of on-demand PrEP could drastically reduce your protection, so it is important to know how to take this regimen correctly.10 If you miss an on-demand dose, you should seek advice from your healthcare provider regarding whether you may need post-exposure prophylaxis (PEP).2

Missed long-acting injectable PrEP

If you’re taking long-acting injectable PrEP, there is a grace period after your scheduled appointment during which you can still receive your injection without it being considered a missed dose.8 If you are still within this period, it's important to speak with your healthcare provider as soon as possible to discuss your options. One of these options may include being given a temporary supply of oral tablets to take until you can reschedule your injection appointment.6,8

However, if you miss your appointment beyond the allowed window, you may need to restart your PrEP injection regimen entirely, based on your healthcare provider’s guidance.8

In general, if you have missed PrEP doses and are concerned about possible HIV exposure, you should speak to your healthcare provider as soon as possible to discuss whether starting PEP is appropriate.2

How to stop takIng PrEP

You can take PrEP for as long as you need/want to, however, if you wish to stop taking it there are safe ways to do so.4,11 It is also important to discuss other HIV prevention strategies with your healthcare provider to ensure you remain protected from HIV.6

You can stop daily PrEP seven days after you last had sex.4

With on-demand PrEP, the final two doses following sex are enough to protect you, so you can stop after completing those doses.2

When you stop taking long-acting PrEP, it continues to provide protection for a certain period of time after your last injection. After this period, drug levels gradually decline.8 If you wish to stop taking long-acting injectable PrEP, you should speak to your healthcare provider regarding how to do so safely because this may vary depending on the type of PrEP you are prescribed.

Abbreviations

PrEP, pre-exposure prophylaxis; PEP; post-exposure prophylaxis

References:

  1. Statpearls. Sundareshan V, Mangat R, Koirala J. Preexposure Prophylaxis for HIV Prevention. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507789/ [Accessed: May 2025]
  2. sexualwellbeing.ie. How to take PrEP. Available from: https://www.sexualwellbeing.ie/sexual-health/prep/how-to-take-prep/ [Accessed: May 2025]
  3. NIH. Pre-Exposure prophylaxis (PrEP). Available from: https://hivinfo.nih.gov/understanding-hiv/fact-sheets/pre-exposure-prophylaxis-prep [Accessed: May 2025]
  4. NHS. How and when to take Pre-Exposure Prophylaxis (PrEP). Available from: https://www.nhs.uk/medicines/pre-exposure-prophylaxis-prep/how-and-when-to-take-pre-exposure-prophylaxis-prep/ [Accessed: May 2025]
  5. UNAIDS. The lens on LEN: The basics on injectable lenacapavir as PrEP. Available from: https://hivpreventioncoalition.unaids.org/en/resources/lens-len-basics-injectable-lenacapavir-prep [Accessed: May 2025]
  6. Apretude. See Boxed Warning | Homepage | APRETUDE (cabotegravir). Available from: https://apretude.com/ [Accessed: May 2025]
  7. PrEPWatch. Lenacapavir for PrEP. Available from: https://www.prepwatch.org/products/lenacapavir-for-prep/ [Accessed: May 2025]
  8. PrEP Guidelines. Injectable PrEP - PrEP Guidelines. Available from: https://prepguidelines.com.au/goals-of-prep/injectable-prep/ [Accessed: May 2025]
  9. Golub SA. PrEP Stigma: Implicit and Explicit Drivers of Disparity. Current HIV/AIDS Reports. 2018;15(2):190-197. doi: https://doi.org/10.1007/s11904-018-0385-0
  10. Grov C, D’Angelo AB, Flynn AWP, et al. How Do Gay and Bisexual Men Make Up for Missed PrEP Doses, and What Impact Does Missing a Dose Have on Their Subsequent Sexual Behavior? AIDS Education and Prevention. 2018;30(4):275-286. doi: https://doi.org/10.1521/aeap.2018.30.4.275
  11. Rainbow Project. PrEP: Everything you’d need to know. Available from: https://www.rainbow-project.org/prep/ [Accessed: May 2025]

NP-GBL-HVX-COCO-250009 | May 2025

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist, or nurse. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the GSK Reporting Tool link https://gsk.public.reportum.com/. By reporting side effects, you can help provide more information on the safety of this medicine.

If you are from outside the UK, you can report adverse events to GSK/ ViiV by selecting your region and market, here.