Pre-exposure prophylaxis (PrEP)
Pre-exposure prophylaxis (PrEP) is a pill that reduces your risk of getting HIV (human immunodeficiency virus). If you have a high enough level of PrEP in your system, it works to stop HIV from getting into your body and making copies of itself. This lowers your chances of getting HIV.
Each PrEP pill contains a mix of 2 drugs, tenofovir disoproxil and emtricitabine. Both of these medicines, given in different doses, are a part of HIV treatment.
PrEP can only be used by people who do not have HIV. It can be used by anyone who has unprotected sex, regardless of their gender or sexuality. If your partner has HIV and has a detectable viral load, then you can use PrEP too.
You need to start PrEP before you have sex. When taken correctly, it’s extremely effective protection against HIV. But it does not stop you from getting other STIs.
Where to get PrEP?
PrEP is now available for free through sexual health clinics.
Find out more about getting PrEP:
Although most people who want to use PrEP are now eligible to get it for free, some people choose to buy it online. IWantPrEPNow have a guide to buying genuine generic PrEP online.
Before you can take PrEP, it’s recommended that you have these tests:
HIV and STI tests - you’ll need these tests regularly once you’re taking PrEP, for example, every 3 months.
a hepatitis B test
a blood test that checks your kidney function - you might need to take this test regularly too, especially if you are over 40 or have existing kidney problems
How to take PrEP
There are different ways of taking PrEP depending on the type of sex you have, how far in advance you plan sex and how regularly you have sex. You can use different methods at different times. And you can use PrEP when you need to - it does not have to be for the rest of your life.
For women having vaginal sex and trans people who have frontal sex or are taking hormone treatment, the recommended way to take PrEP is daily.
If you only have anal sex, you can choose between taking PrEP daily or taking it on demand when you plan to have sex. This is also called event-based dosing or event-based PrEP.
Talk to your clinic to decide the best method for you.
Daily PrEP - 1 pill a day
Taking PrEP daily gives protection for both anal and vaginal sex. You need to have taken a pill every day for 7 days to be fully protected for vaginal or frontal sex.
If you have anal sex only, you can start daily PrEP by taking 2 pills, 2-24 hours before having sex. Then take the pills daily.
You can take the pill at any time of day but try to do it around the same time every day so it becomes routine and you’re more likely to remember.
Event-based or on-demand PrEP
This method is not suitable for people having vaginal sex. Only use on-demand dosing if you have anal sex.
With event-based PrEP, you must not miss any pills. And you need to know when you plan to have condomless sex.
To use PrEP on demand:
take 2 pills, 2-24 hours before having sex
after sex, take 1 tablet every 24 hours until you’ve had 2 days without sex
Side effects of PrEP
You might notice one or more of these common side effects, especially in the first few weeks of taking the medication:
feeling or being sick (nausea or vomiting)
bloating and indigestion
feeling dizzy or weak
insomnia (trouble sleeping)
These side effects will not damage your health, but they can be hard to live with. The NHS website has advice for managing these side effects. If they really bother you or they do not go away after your first month on PrEP, talk to your clinic for advice.
People rarely experience more serious side effects. But PrEP can affect your kidneys. As part of getting PrEP, you need to have kidney tests done before and during your treatment.
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