PrEP – What You Need To Know

The GMHS is currently providing an ongoing limited service. They are currently taking bookings for their PrEP service and also for their asymptomatic screening service. Bookings are by email only to:


A list of alternative available PrEP clinics around the country can be found at:


A list of STI clinics is available here


While waiting for a PrEP appointment and to reduce your risk of HIV, always use a condom.

What is PrEP?

PrEP (Pre-Exposure Prophylaxis) is a HIV prevention strategy that involves HIV negative people taking ARVs (antiretroviral drugs) before and after sex to dramatically reduce the chances of sexually acquired HIV infection.

Results in clinical studies have been overwhelmingly successful and so the effectiveness of PrEP is now widely accepted in significantly lowering the risk of becoming HIV positive.

The medication used for PrEP is a tablet which contains two drugs; tenofovir and emtricitabine. This drug is marketed as Truvada but increasingly, generic versions of PrEP have been made available throughout Europe. 

How does PrEP work?

PrEP works by stopping the HIV virus from replicating in your body. When the virus cannot replicate it cannot establish an infection.

If you are taking PrEP properly and are exposed to HIV, the drug will stop the virus from replicating and you will remain HIV negative.

How often do you take it?

PrEP is licensed for daily use but studies have shown that it can be effective when taken ‘on demand’. However, if you are a trans man you must take PrEP as a daily pill and not the ‘on demand’ option. 

The two ways to take PrEP are:


  • Take one pill every day.
  • You need to take one pill every day for 7 days before it becomes fully effective.
  • Daily PrEP is suitable for anal and vaginal sex.
  • It is best to take your pill at the same time every day so that it becomes routine, but a few hours early or late is fine.
  •        Daily PrEP is recommended if you are a trans man.

On Demand

  • If you know that you might have condomless anal sex in the next 24 hours
  • Take two pills between 2-24 hours before sex,
    Take one tablet 24 hours after that
    Take one more pill 24 hours after that
  • If you are having sex for an extended period of time perhaps over a few days or a weekend, continue to take a pill every 24 hours until you have 2 sex free days.
  • On demand PrEP is only suitable for anal sex
  • On demand PrEP is not suitable if you have an active Hepatitis B infection.
  •        On demand PrEP is not suitable if you are a trans man.

Who is PrEP for?

PrEP is a great prevention option for people who are HIV negative and have sex without condoms or have sex in situations where condoms are not available or not easily used at the time.

PrEP is suitable for anyone at risk of HIV infection. This includes men, women, trans people, non-binary people and those in a relationship with an HIV positive partner who does not have a undetectable viral load.

Other factors are related to a higher risk of HIV. These include:

  • A recent STI (especially rectal infection or syphilis).
  • Recent use of PEP (post-exposure prophylaxis).
  • Using some recreational drugs sex (crystal meth, mephedrone or GHB) – also known as Chemsex drugs.

Any of these mean you are likely to benefit even more from taking PrEP.

Where do I get PrEP?

PrEP is now available through the HSE free of charge to those who are considered to be at high risk of contracting HIV through sex.

Click on the following link to find out where you can get PrEP.

For all updates on this programme please visit

We recently updated our information about getting PrEP online. You can read that here.

In Ireland, it is illegal to supply medication by mail order, including over the internet. The Health Products Regulation Authority provides information for the public in relation to sourcing medication over the internet which is available here.

What you need to do before taking PrEP?

Please talk to a health advisor, nurse or doctor at the clinic. They can help you if you are planning to take, or are already taking PrEP.

It is really important to have an HIV test before or as you start.

PrEP can only be used if you are HIV negative. If you are already HIV positive and don’t realise it, you could develop resistance to drugs that you will need for treatment.

Ask for a ‘4th generation’ HIV blood test. This is also called a ‘combined antigen/antibody’ test. This tells you your HIV status approximately 4 weeks ago. Most finger prick tests are currently ‘3rd generation’. They tell you your HIV status approximately 3 months ago. So don’t rely on a fingerprick test alone before you start PrEP.

If you are just starting PrEP and had a risk in the last 4 weeks, have another 4th generation HIV blood test 4 weeks after starting, just to be sure an early infection was not missed. Don’t start PrEP if you have flu-like symptoms and a recent HIV risk. This is to check that these symptoms are not related to a recent HIV infection (ie seroconversion).

If you are starting PrEP after PEP, it is best to start immediately if you have ongoing risks. Ideally you should have an HIV blood test around the time you finish PEP/start PrEP plus another HIV blood test 4 weeks into PrEP.

Remember that unprotected sex while taking PrEP will reduce your risk of HIV but not other STIs, use condoms to reduce your risk of other STIs.

You will also need to have your kidney function checked. Kidney monitoring just involves a blood test for creatinine, and a urine test for protein. These should ideally be done just before or on the day you start.

You will need to be tested for Hepatitis B as PrEP is also active against the Hepatitis B virus.

What you need to do while taking PrEP

Once you have started PrEP, monitoring is important.

Every 3-4 months:

  • Have a ‘4th generation’ HIV blood test. This is also called and ‘antigen/antibody’ HIV blood test.
  • Have a full screen for other sexually transmitted infections (STIs).
  • Have a urine dipstick test for protein when you have your STI check up; if there is more than a trace, an additional blood or urine test can be sent off for kidney function.

Every 12 months:

  • Have a blood test to check your kidney function.
What about other sexually transmitted infections?

Research has shown that PrEP is highly effective at preventing HIV as long as it’s taken as directed.

However, PrEP will not protect you from other sexually transmitted infections (STIs) whereas condoms will. If you’re using PrEP it’s important that you go for regular STI screens every three months so you can get any other infections treated.