There are 2 ways you can take HIV PrEP, called daily dosing and event based dosing. Event based dosing is sometimes called on-demand dosing. You can change between daily and event based dosing. But speak to your sexual health service first. They'll support you to make changes safely.
Daily dosing means you take 1 tablet every day. Taking HIV PrEP every day ensures protective levels of HIV PrEP in your body 24 hours a day, 7 days a week. If you’re more likely to have unplanned sex or cannot predict when sex is likely to occur, daily dosing provides the best protection. You'll be protected once you've taken 7 HIV PrEP pills in a row.
Event based dosing works when you know when you’ll be having sex and can plan in advance. Event based dosing should only be used if your only risk of getting HIV is from anal sex. Event based dosing is when you take HIV PrEP pills before and after each episode of sexual activity. This means you:
- Take 2 tablets of HIV PrEP before you have sex. Ideally this should be between 2 and 24 hours before sex.
- Take 1 tablet of HIV PrEP every 24 hours until you've had 2 sex free days.
Event based dosing is not an option if you have hepatitis B.
Download the event based dosing diagram (PDF, 250 KB)
Choosing the right dosing for you
How you take HIV PrEP depends on what type of sex you have and your own personal preferences.
The doctor or nurse at the sexual health clinic will:
- discuss what’s important to you
- make sure you feel confident with your chosen option
- make sure you know how to take HIV PrEP
Missing a dose of your HIV PrEP may put you at risk of getting HIV, so it's important to take PrEP as advised. Setting mobile phone reminders can be a simple way to help you keep track of when you take your HIV PrEP.