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How to take PrEP

How to take PrEP

Updated on:
February 28, 2023

Daily PrEP pills

The most effective method of taking PrEP medication is to take one PrEP pill every day. Daily PrEP is up to 99% effective in preventing HIV for gbMSM folks when taken consistently and correctly.

You should be taking one dose of PrEP at the same time every day in order to receive maximum benefit.

There are three PrEP pill options that all offer the same amount of protection against HIV: Truvada, generic Truvada, & the Descovy prescription.

Missing a PrEP dose

If you miss a dose, do not take a double dose. Doubling up does not increase the effectiveness of daily PrEP, but it does increase the likelihood that you will experience a side effect from PrEP. Missing one dose does not significantly decrease your level of protection.

If you have missed a dose and it has not been more than 12 hours since you were scheduled to take it, you should take it as soon as you remember.

If you have missed a dose and it has been more than 12 hours since you were scheduled to take it, do not take your dose for that day - wait, and simply take your next dose when you are scheduled to do so the following day.

If you are unable to take your daily dose at your usual time, aim to take it as close to the same time as possible.

If you are travelling to a different timezone, make sure you take the time difference into consideration when you take your next doses while you are away from home. For example, if you lived in Calgary, Alberta and usually take your PrEP at 8:00am MST, if you were to travel to Toronto, Ontario, you would want to take your PrEP at 10:00am EST in order to ensure you remain on the same schedule.

Stopping PrEP

Current studies suggest that it is safe to stop taking PrEP between 2 and 28 days after your last possible HIV exposure. Unfortunately, there isn’t enough evidence to support that it is enough to only take PrEP for 2 days post-exposure, and most experts recommend a full 28 days.

Some people consider stopping PrEP if they feel they are no longer at a substantial risk of contracting HIV, but there are other reasons an individual may feel that they would like to come off of PrEP. Whatever the reason may be, it is best practice to follow up with your clinician to inform them of your concerns and considerations so they can help you assess your risk and provide you with personalized medical advice to empower you to make a well-informed, confident decision.

Tips on taking PrEP

As a Freddie patient, you will have access to a pill counter on your dashboard in your patient portal at To make sure you receive your lab requisitions at the appropriate time to get your follow-up testing done in time for receiving your refills, it is a good idea to log in to your account every once in a while and make sure that your pill counter has been adjusted to accurately reflect the number of doses you have remaining.

When you receive your prescriptions, you may want to set up a calendar event in your phone to notify you when you are getting down to your last two weeks of that refill. This will help you remember that you are running low and that you should book a lab appointment for follow-up testing in order to get your next refill. You will need to log in to your Freddie patient portal to check for your new lab requisition as well, and to complete a short self-assessment.

A couple tips to help you remember to take PrEP at the same time every day include the concept of “habit-stacking” and creating a visual reminder for yourself by putting your pill bottle in a place that you will see it as you go about your daily routine.

Habit-stacking is a method of introducing something new to your daily routine with less conscious effort. For example, if the first thing you do every morning is make a pot of coffee, put your pill bottle on top of your coffee machine where you will be forced to move it before you can go on with your usual routine. If you can integrate taking your PrEP pill at the same time as completing something you already have a scheduled daily routine for, it’ll be easier to avoid missing doses.

Are you considering PrEP? We’ve compiled guides on PrEP costs, financial assistance programs, and a list of providers in each of the following cities:

On-demand / event-based PrEP

On-demand/event-based PrEP is a method of HIV prevention that involves taking pills on days before and after having sex. This intermittent method of taking PrEP may be an option for gbMSM folks who know when they will be having sex, as it requires some planning to ensure it is effective in preventing HIV transmission.

In order for event-based PrEP to be effective, two pills must be taken 2 to 24 hours before an upcoming sexual encounter. Post-encounter, one pill must be taken daily for 2 days. If a person has multiple sexual encounters for several days in a row, they should be taking one PrEP pill every 24 hours until 2 days after the last time they had sex.

Evidence has shown that intermittent use of PrEP is effective in reducing the risk of HIV transmission among gbMSM populations, and it is important to note that there have not been any studies conducted to evaluate its effectiveness in other populations and is therefore not recommended for people who have vaginal sex or people who inject drugs.

Reviewed by:
Dr. Caley Shukalek

Caley is passionate about evidence-based, patient-centred care, including telemedicine that can provide high quality care from wherever a patient may choose.

He helped create Alberta's PrEP guidelines and works as a specialist in General Internal Medicine with additional training in sexual health, including HIV and sexually transmitted infections.

He holds an Masters of Public Health from Johns Hopkins University, an MD from the University of Calgary and an MSc from the University of Alberta.