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PrEP (Pre-Exposure Prophylaxis) for HIV

PrEP (Pre-Exposure Prophylaxis) for HIV

Updated on:
May 2, 2022

What is PrEP?

PrEP for HIV is short for pre-exposure prophylaxis. PrEP is a once-per-day HIV prevention pill that reduces the risk of contracting HIV by up to 99%. If you take a PrEP prescription daily, the presence of the medicine in your bloodstream helps stop HIV from taking hold, ensuring you remain HIV negative.

How does PrEP prevent HIV?

PrEP medication stops HIV in your bloodstream from replicating, eliminating the virus from your body when the original exposure amount dies. 

Essentially, PrEP works by ensuring HIV cannot replicate in your body and ensures you remain HIV negative.

Who can use PrEP?

PrEP is intended for those who are HIV negative and are at an elevated risk of contracting HIV. You may want to consider PrEP if you:

  • Have condomless anal or vaginal sex
  • Have a sexual partner who participates in condomless anal/vaginal sex
  • Use, or have a sexual partner who uses injection-based drugs
  • Have a sexual partner who is HIV positive
  • Have anal or vaginal sex with multiple partners
  • Participate in sex work that involves anal or vaginal sex
  • Recently were diagnosed with a sexually transmitted infection (STI)

When speaking with a medical professional about HIV & prevention, it is important to be as honest as possible about your sexual history. This open conversation allows for a more accurate evaluation of your medical needs, including PrEP.

How effective is PrEP?

PrEP effectiveness for sex

When PrEP is taken daily as prescribed, it reduces the risk of contracting HIV by 99%. ​​

If PrEP is taken four times a week, it’s 99% effective at preventing HIV infection through anal sex. If taken only two times a week, efficacy against HIV drops to 75%.

When taken correctly, PrEP on-demand, also known as the 2-1-1 method, has shown an overall efficiency of 86% in preventing HIV among MSM (men who have sex with men). Though it’s recommended to talk to your doctor before switching to PrEP on-demand.

Condoms & daily PrEP are recommended for both insertive and receptive partners to maximize protection against  HIV & other STIs.

PrEP effectiveness for drug injection

​​People who share injection drug equipment like needles, cookers, filters, and water, are at an elevated risk for contracting HIV. The best tactic to minimize HIV risk during drug injection is to use new equipment every time you inject. Do not re-use or share your injection equipment with others.

For daily PrEP users, studies have shown that it can reduce HIV risk by 84% from drug injection.

If you inject drugs and are thinking about starting PrEP for HIV prevention, it’s important to consider your ability to safely store the PrEP medication and take it daily.

Common PrEP side effects

Short term side effects

Usually, less than 10% of patients on PrEP experience any side effects. For those who do experience side effects, they tend to go away within 1-2 weeks naturally. Before receiving a prescription, lab tests are required to help ensure your body can tolerate PrEP.

Possible short-term side effects of PrEP medication include:

  • nausea
  • headaches
  • diarrhea
  • vomiting

Long term side effects

In a small number of people, PrEP has been tied to a decrease in kidney and liver function, and bone density.

Fortunately, even in these cases, toxicity levels did not increase the patient’s risk of kidney or liver failure, or bone fracturing. These changes were reversed after they stopped taking PrEP.

Regular lab testing every three months while on PrEP is crucial to ensure that your body can safely tolerate the medication.

Is PrEP safe?


If HIV is contracted during pregnancy or while chestfeeding, there is a higher risk of transmitting HIV to the newborn. Fortunately, daily PrEP use is safe for both the parent and the baby while pregnant and chestfeeding.

HIV positive individuals

People can develop a resistance to the drugs in PrEP if they are HIV positive and unaware of their HIV status. Developing resistance to these active drugs can reduce a person’s future HIV treatment options. PrEP is only recommended for HIV negative individuals.

Interactions with other medications while on PrEP

Most commonly used medications and recreational drugs are not known to interact with PrEP, but there are some. 

Of the substances that interact with PrEP, Non-steroidal anti-inflammatory drugs (NSAID) are the most frequently used and should be avoided if possible. If pain-relief medicine is needed, acetaminophen (Tylenol) should be taken instead of ibuprofen (Advil), acetylsalicylic acid (Aspirin), or naproxen (Aleve) whenever possible.

Hormone replacement therapy (HRT)

People of all genders can use PrEP. PrEP components do not interact with hormones that some trans people take; however, studies including trans people are few and sparse. 

There is some evidence that feminizing hormones taken by some trans women can lower the amount of PrEP drugs by a small amount in your body. This same evidence shows drug levels are still high enough to protect against HIV transmission, but making sure you take PrEP exactly as prescribed is that much more important to ensure its effective.

PrEP is highly effective when taken consistently and correctly by trans and gender diverse people.

Pre-existing conditions

Existing deficiencies in kidney or liver function, or bone density, can sometimes act as a barrier for those trying to get on PrEP. These deficiencies can cause a person’s body not to be able to tolerate the active ingredients in Truvada and generic PrEP (generic Truvada).

Luckily the Descovy pill has now been approved as a form of PrEP in Canada and is a safe alternative for those with pre-existing kidney or bone deficiencies. As with any individual, it’s always best to consult with a medical professional before starting PrEP, as each case is unique.

How much does PrEP cost?

The price of PrEP varies depending on where in Canada you live.

In some provinces, the provincial government covers the cost of PrEP for eligible residents. In others, the price of PrEP may only be covered by provincial programs for some residents. 

Fortunately, Freddie offers financial assistance for PrEP with our Compassionate Careand Bridging programs to increase access to PrEP in Canada! 

Over 90% of Freddie patients receive PrEP + discreet delivery for free in Canada. Take our free, 1-minute evaluation to see an estimate for how much PrEP would cost you.

How to get PrEP in Canada

To get started on PrEP, you’ll need to go through the following steps:

  1. Speak with a healthcare provider to make sure that PrEP is a fit for your health needs. They will then refer you to a lab for testing.
  2. Complete lab work to test for HIV & your kidney function to make sure that your body can safely tolerate the medication.

Finding a medical provider to talk in person to can often take time to schedule. Luckily at Freddie, we make accessing PrEP as easy as possible by offering you the ability to manage your whole PrEP prescription process online with our team of trained medical professionals.

If you’d like to get started immediately, complete our 1-min assessment questionnaire and schedule your free online consultation with one of our clinicians today. 

You can also speak with your personal physician or visit a PrEP provider if you’d like to get a prescription in person.

Different types of PrEP

In Canada, three different medications act as PrEP for HIV

Generic PrEP, nicknamed “generic Truvada”

Truvada and generic PrEP (“Generic Truvada”) contain the same two anti-HIV drugs as active ingredients: tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC).


Similar to generic PrEP, Truvada also contains two anti-HIV drugs as active ingredients: tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC).


Descovy contains two anti-HIV drugs as active ingredients as well, but it’s the first medication offering a different component: tenofovir alafenamide (TAF) and emtricitabine (FTC).

Descovy was created to combat the negative effects Truvada & generic PrEP may have on kidney and bone health. This was accomplished through the development of a new formulation of tenofovir called TAF (tenofovir alafenamide).

Cost differences between Generic PrEP, Truvada, and Descovy

Of the three types of PrEP medication, generic PrEP is the cheapest option and can often be obtained for free or low-cost. This is also the PrEP medication that Freddie prescribes online.

Truvada is approved for use in Canada but is not covered by provincial health plans. As a result, out of pocket costs, even with private health insurance, non-generic Truvada can be as much as $300/month.

​​In Canada, Descovy is not covered by provincial health insurance, and out-of-pocket costs are at least $1,000/month.

All three PrEP pills offer similar levels of protection against HIV (99% effective) when taken daily. The primary differences between the three forms of PrEP are financial accessibility due to differing coverage from insurance & Descovy having fewer reported side effects.

Getting started on PrEP

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

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

For anal sex, PrEP is highly effective after taking it for 7 days consistently. For vaginal/frontal sex, PrEP takes around 3 weeks (21 days total) to reach desired concentrations for protection against HIV.

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. It is recommended to wait a full 28 days after your last possible HIV exposure to stop taking PrEP so that you can minimize HIV risk as much as possible.

Some people consider stopping PrEP if they feel they are no longer at a high 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 make a well-informed decision.

Other common questions about PrEP for HIV

Can I get PrEP for free?

With Freddie’s financial assistance program subsidizing PrEP costs, over 90% of Freddie patients obtain PrEP for free. You can book a free consultation by answering this 1-minute PrEP questionnaire to see if you qualify for free PrEP. We’ll do our very best to help you find PrEP for free or as low cost as possible.

For a breakdown of where you can get PrEP free in Canada, check out our PrEP cost breakdown by province article.

How do I buy PrEP?

Freddie’s online services allow you to access PrEP care from the comfort of your home, guaranteeing that you’ll be speaking with a competent team of trained and inclusive medical providers.

You can also access PrEP from a local PrEP provider. Here’s a list of PrEP providers by city:

What exactly does PrEP do?

PrEP or pre-exposure prophylaxis is a pill taken daily, orally, that reduces the risk of getting HIV by 99%

Is PrEP safer than condoms?

PrEP reduces HIV risk by 99% when taken as prescribed, but it does not prevent other STIs. Condoms, when used consistently and correctly, prevent the transmission of HIV by 98%. It is recommended to use both PrEP and condoms for maximum protection.

Who should use PrEP?

PrEP is for anyone who is HIV negative considered at higher HIV risk, like men who have sex with men, transgender women, people who use drugs, and racialized communities. Inconsistent condom use and drug use can also increase one’s HIV risk.

What drug is PrEP?

PrEP is an HIV prevention method that uses a combination of anti-HIV drugs—usually composed of two chemicals: tenofovir and emtricitabine.

Can I buy PrEP over the counter?

HIV PrEP is only offered as a prescription medication that cannot be bought over the counter. With Freddie, you can easily speak to a provider, access your requisition, and have an accessible hub for your PrEP care, all kept confidential and safe. You can also talk to your family doctor or go to a sexual health clinic near you.

Does PrEP help against Covid?

There is no evidence that the use of PrEP can either treat or prevent Covid-19.

Does PrEP make you ill?

Usually, only 1-10% of patients experience any short-term PrEP side effects. For those who do experience short-term side effects from PrEP, they tend to go away within 1-2 weeks naturally. Potential side effects include nausea, headaches, diarrhea, and vomiting.

In a small number of people, PrEP has resulted in a decrease in kidney and liver function, and bone density. Even in these cases, toxicity levels did not increase the patient’s risk of kidney or liver failure, or bone fracturing. These changes were reversed after they stopped taking PrEP.

Does PrEP interact with the Covid vaccine?

There is NO evidence of interaction between PrEP and any COVID vaccines approved in Canada. In other words, there is no reason that being on PrEP should stop you from getting vaccinated or that being vaccinated should stop you from being on PrEP. We encourage you to get the vaccine to protect yourself and everyone around you.

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.