PrEP’s effectiveness is directly related to taking the pill at around the same time everyday. If you take it daily and never miss a dose, it works amazingly well. If you miss a few (or more) doses, it works less well. It also takes about a week for people having receptive anal sex, and about 21 days for people having receptive vaginal sex before they’re fully protected. If you’re going off PrEP you need to take it for four weeks after the last time you had sex for that encounter to be protected.

It’s very rare, but some strains of HIV are resistant to PrEP. There have been a few reported cases of people who took PrEP as prescribed becoming infected with these strains of HIV.

PrEP works great in combination with other strategies. Using barrier protection when you’re on PrEP may seem unnecessary, but makes the possibility of HIV transmission virtually zero. This is especially important if you or your partner isn’t taking PrEP consistently. Condoms also protect against many other STIs and can be used as a method of contraception. Likewise, when people on PrEP have sex with partners that have undetectable HIV viral loads, based on research to date the possibility of HIV transmission is zero.

It is recommended that PrEP be used in addition to condoms, so you can ensure that the chance of HIV transmission while taking PrEP remains extremely low, especially if pills are missed. Neither PrEP or condoms are 100% effective, so using both can be a great way of staying HIV-negative. At the same time, PrEP is recommended for people who are not using condoms, so it’s important to know that PrEP still works really well on its own.

If you want to decrease the chance of getting some other STIs like chlamydia, syphilis, or gonorrhea, condoms provide that protection. Check out our page about combining sexual health strategies to figure out which ones will work best for you.

If it happens, take your next pill as soon as you remember. Don’t bother taking two pills at a time to make up for it though. If you don’t generally use condoms during sex, it might be a good idea to use condoms for the days/weeks after a missed pill to keep yourself extra safe.

This could mean a few things and it’s best if you follow up with your doctor right away. If you have flu-like symptoms, like a fever, a headache, joint pain or a sore throat, it could be a sign of possible HIV infection. If you have stomach aches or nausea, these could be side effects of the drug. If they’re really bad, or haven’t gone away after a while, talk to a doctor.

While rare, PrEP can cause bone mineral density and kidney problems for folks who have pre-existing conditions related to their bone mineral density and kidney. If you’ve had any related issues, it is a good idea to talk to your doctor to figure out if there are ways to minimize the impact of PrEP.

PrEP can be a complicated issue if the person using it also has a hepatitis B infection. It is especially important that you inform your doctor that you have hep B and talk about what that means.

It’s also important to tell them about any meds, including vitamins and supplements, that you take regularly, or any other health stuff they might not know about you.

Taking daily PrEP looks different for everybody. Some people might take it for a couple months when they feel it is appropriate, or others might take it over a longer-term. What’s important is that it takes about a week of taking PrEP daily to be effective in the anus/rectum, 2-3 weeks in the vagina, and you’d need to take PrEP for 28 days after the potential exposure.

While it’s always a good idea to plan ahead to prevent HIV, PrEP works best as a long-term routine and not as an occasional thing. Some people think that short-term or casual PrEP treatments work, which some people call “disco dosing” or “condom holidays.” In terms of timing, it takes about a week of taking Truvada daily to be effective in the rectal tissue, up to 3 weeks in vaginal tissue, and you’d need to take PrEP for 28 days after the potential exposure.

There is a method called the 2-1-1 method, which involves taking PrEP 4 times, twice within 24 hours of having sex (24 hours, and 2 hours before) and then 1 time 24 hours after sex, and another time 48 hours after sex. This method, though less effective than daily PrEP use, has been shown to be quite effective in gay and bisexual cis men who have sex with cis men, although it is unclear how effective it is in other populations, and if certain bodies or sex acts are more or less protected through this strategy. If you are a cis man who is having sex with men, it may be worth exploring this strategy as a more cost effective strategy, but it has not yet been shown to be a reliable strategy for folks outside of that demographic.

Currently in Canada, PrEP is approved for daily use in combination with other strategies. If you want PrEP to work best, getting a prescription in the long-term is a more stable and dependable option.

If you become HIV-positive, you’ll have to stop taking PrEP immediately and start a new treatment for HIV infection. Check out our HIV treatment section to learn more about what to do after testing positive for HIV.

First, if you feel that PrEP is the right choice for you we recommend taking some time to ensure you have explored all your options. Talk to your healthcare provider, or reach out to us at HEAL NS to talk about what coverage programs might be available to you.

If you are unable to access PrEP, take some time to learn more about other HIV prevention methods. You might explore other ways to use barrier protection methods, find out where to get clean drug supplies through local harm reduction centers, learn about PEP, and practice having safer sex conversations with partners. These are all great ways to take control of your sex life without going on PrEP.

There is a lot of confusing information and misinformation online about whether PrEP is effective in trans and nonbinary folks who are either on hormones or have had gender-affirming bottom surgeries. This is largely due to the fact that research often excludes trans folks, or doesn’t collect information that is specifically relevant to trans and nonbinary people.

Understanding the effectiveness of PrEP is, in some ways, more complicated than it seems. You have to factor in, not only the effectiveness of the drug, but its interactions with other drugs/hormones/medications, the body parts that are or aren’t being exposed to HIV, how regularly someone takes their PrEP prescription, and the social and systemic factors that influence a person’s access to PrEP/ability to take it consistently.

PrEP is highly effective, and the vast majority of research that has been done suggests that taking hormones or undergoing gender-affirming surgery, doesn’t significantly reduce its effectiveness. There was also a myth spread at one point that taking PrEP could reduce the effects of hormone therapy, especially testosterone. This has been disproven!

All of that is to say – if you are trans and in a higher risk demographic you shouldn’t hesitate to reach out to your doctor or a healthcare provider to assess if PrEP might be right for you.

PrEP can be hard to access, especially for trans folks, so check out our section on how to access PrEP to learn more about what options might be available for you. You can also check out our sections on advocating for yourself if you are looking for tips on how to approach difficult conversations around identity and HIV.

To hear from some trans people on what taking PrEP has been like for them, you can check out this great video by My Genderation.