PrEP 101

The information in this post is predominantly based on information provided from The Terrance Higgins Trust, CliniQ, HIVE, Project Inform,, and the advice of my GP when I started taking PrEP. Where sources have come into conflict, the position of the more recent resource has been taken to be correct, and sources published by medical or activist groups are prioritized over the advice of my GP.

I am not a medical professional, and I recommend discussing PrEP with your medical provider. This blog post is provided as a collection of information only.


What is PrEP?

PrEP stands for Pre Exposure Prophylaxis. It is the use of HIV medications by HIV negative people to prevent themselves contracting HIV. It is not the same as Post Exposure Prophylaxis (PEP), which is a treatment that can be taken after sex to help prevent HIV contraction.

The only medication approved for PrEP is Truvada, and its generic versions. PrEP was approved in the US in 2012 and in Europe in 2016.

PrEP does not protect against other STIs or unwanted pregnancy. You may choose to use PrEP in combination with condoms, hormonal birth control, or other prevention strategies.


Is PrEP Right for You?

Only a medical provider can answer this question fully. Before you can take PrEP, you should visit your GP to:

  • Find out if you are HIV negative. PrEP is only usable by those who are HIV negative. Remember that HIV tests do have window periods, and that if you have taken risks recently, you may have to wait to be tested to be sure your results are accurate.
  • Have your kidneys checked. PrEP may worsen the conditions of the kidneys in some people, so if you have kidney or bone problems, it may be an issue of concern. Your GP likely will want to do regular monitoring of your kidneys when you are on PrEP
  • Be tested for Hepatitis B. While you can still use PrEP if you have Hep B, you will need extra guidance, as PrEP drugs are also active against Hep B

However, PrEP may be of particular interest to those who fall into one or more of the following groups/categories:

  • Men who have sex with men (including trans men and other transmasculine people)
  • Sex workers
  • People in a mixed status relationship (i.e. a relationship where one or party is HIV positive, while the other/s are not)
  • Trans women who have sex with men

A free tool from the U.S. Center for Disease Control can suggest if PrEP is right for you. You can find it here. However, do note it does not consider trans status a factor in suggesting if PrEP is right for somebody.

A leaflet by HIVE online has been produced for men who have sex with men (MSM) considering PrEP. This leaflet is trans inclusive, and can be found online here.


PrEP and Transmasculine People

There is an unfortunate gap in knowledge when it comes to PrEP and transmasculine people. No clinical trials to date have included transmasculine people as a group, where they have included cis men, cis women, and transfeminine people. In studies where men who have sex with men (MSM) are included, trans MSM are often excluded.

However, while there are not definitive guidelines, some suggestions for transmasculine people intending to take PrEP can be given.

PrEP does not interact with HRT. It also does not interact with hormonal birth control, and you can safely use both together. Information about birth control options for transmasculine people can be found here


How to Take PrEP

How you should take PrEP depends on what kinds of sex you are engaging in.

  • If you intend to have receptive vaginal sex, taking a daily dose of PrEP is recommended.
  • If you have had phalloplasty, and engage in penetrative sex, a daily dose of PrEP is recommended.
  • If you only have receptive anal sex, you can use a daily dose, or on demand dosing.

Daily Dose PrEP

Daily dose PrEP is pretty self explanatory. You take one pill of PrEP every day. 7 days of PrEP is required as a lead in time. This is the kind of dosing I personally use. PrEP can be taken at any time of the day, and can be taken with or without food.

I find that taking my PrEP pills at the same time each day, incorporating it into my routine, made me more likely to remember to take it. I place it next to my toothbrush in the evenings, ready to take in the mornings.

Missing one or two pills should not affect your treatment’s efficacy. However, if you miss three or more tablets in the week before a risk, you should visit your sexual health provider to discussion the option of post exposure prophylaxis (PEP), and follow up screenings.

On-Demand PrEP

On-demand PrEP is not recommended for those having vaginal sex, or for people who have had phalloplasty. It only provides adequate protection for those who have receptive anal sex.

On-demand PrEP does require some thought about how to make PrEP effective. Enough medication needs to be in your body at the time of risk.

A double dose (two tablets) needs to be taken at least 2 hours before exposure, or up to (and ideally) 24 hours. You can start taking pills up to a week before the event with a risk of exposure, so long as you take PrEP daily after this.

A second dose (one tablet) should be taken 24 hours after the double dose. If you are still at risk during this period, you should continue to take a dose (one tablet) of PrEP every 24 hours while that risk continues.

After the last risk, you should take a dose (one tablet) every 24 hours for at least 48 hours after your last risk.

Examples of how on-demand dosing could look include:

  • A person takes a double dose of PrEP on Friday at 11am. They engage in activity with a transmission risk several times between 6pm on Friday and 6am on a Sunday. They take one dose of PrEP at 11am on Saturday, Sunday, Monday, and Tuesday.
  • A person takes a double dose of PrEP on a Monday at 9am. They continue to take a (single) dose at this time each day. On Wednesday at 5pm, they engage in activity with a transmission risk. They continue to take a dose at 9am on Thursday, Friday, and Saturday.



Accessing PrEP in the UK

PrEP on the NHS

Currently, PrEP is available through the NHS if you live in Scotland or Wales. There are criteria for eligibility:

  • You must be 16 years old, or older in Scotland. You must be 18 years old, or older in Wales.
  • You must have a confirmed HIV negative test in a sexual health clinic
  • You must be able to attend regular 3 month reviews
  • You must be resident in Scotland or Wales.

One or more of these criteria must also apply:

  • You are a partner of a person who is HIV positive and has a detectable viral load.
  • You have a documented bacterial rectal STI in the last year, and are a trans women, or a man (cis or trans) who has sex with men
  • You have had condomless penetrative anal sex with two or more partners in the last 12 months, are likely to do so again in the next three months, and are a trans women, or a man (cis or trans) who has sex with men
  • You are part of another population at similar high risk of HIV acquisition, such as sex workers

More information on accessing PrEP on the Scottish NHS can be found at Prep.Scot. Information on accessing PrEP in Wales as part of the PrEPARED study can be found at FriskyWales, including a list of clinics.

Northern Ireland currently has no PrEP Provisions.

In England, you can access PrEP as part of the PrEP IMPACT study. However, this is limited to 10,000 people. Information on accessing PrEP in England can be found at the PrEP IMPACT website.

PrEP Off the NHS

Private prescriptions for PrEP are an option. This normally costs around £400 a month, but some clinics offer it for less. Currently I pay £55 for a month of PrEP.

You can also buy PrEP on the internet. It is legal to buy and import PrEP if it is for personal use. It’s recommended that you don’t buy more than three months worth at a time.

There are always risks when buying medication online, but you can reduce these. only provides information of pharmacies that have been verified.


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