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Sexual and Reproductive Health

HIV Pre-Exposure Prophylaxis (PrEP)

​​Human immunodeficiency virus (HIV) attacks the immune system and makes it hard for the body to fight diseases and infections. HIV is passed (transmitted) through blood, semen, and fluids from the vagina and rectum.

HIV pre-exposure prophylaxis (PrEP) helps prevent HIV in people who may be more likely to come into contact with the virus. It is taken as a pill 1 time every day.

Who can benefit from HIV PrEP

HIV PrEP is for people who are HIV negative and who have more or ongoing chances of getting HIV.

This includes:

  • men who have sex with men, transgender women, and gender diverse people who have had anal sex without a condom in the past 6 months and who have any of the following:
    • chlamydia, gonorrhea, or syphilis infection in the past 12 months
    • a sex partner living with HIV who is not taking treatment, has HIV virus in their blood, or doesn’t know their HIV virus levels
    • multiple sex partners
  • anyone in an ongoing relationship with a partner who is living with HIV and who is not taking treatment, has HIV virus in their blood, or does not know their HIV virus levels
  • people who inject drugs and share injection supplies
  • inject drugs and share needles or other drug equipment
  • anyone who has sex with a partner or partners from a population or community with high rates of HIV

HIV PrEP may not be necessary if you are in a closed relationship with a partner who does not transmit HIV (undetectable viral load).

Undetectable viral loads

People with very low levels of HIV in their blood have an undetectable viral load. This means that the level of HIV in their blood is so low that a viral load test won’t detect that they have HIV. If your partner has an undetectable viral load, they won’t pass HIV to you through sexual activity. This is called U=U which means HIV that is undetectable is untransmissible and can’t be passed from one person to another through sexual activity.

How well HIV PrEP works

HIV PrEP lowers the risk of getting HIV from sexual activity by more than 95% when it’s taken every day. It uses tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) (a combination of medicines that is also called TDF/FTC or Truvada). These are the same medicines used to treat HIV. HIV PrEP stops the virus from making copies of itself (multiplying).

The medicine doesn’t work right away to protect you, so it’s important to use condoms or avoid having sex for at least:

  • 7 days, if you have anal sex
  • 20 days, if you have vaginal sex

HIV PrEP works best to help prevent HIV when you also talk openly with your sex partners about their HIV status, use condoms, and have regular testing for sexually transmitted infections (STIs).

​Starting HIV PrEP

Talk to your healthcare provider if you want to start taking HIV PrEP. They will need to look at your vaccine history and send you for tests that check for HIV and other STIs, liver infections (called hepatitis), pregnancy, and tests to see how well your kidneys are working.

Once your healthcare provider has all of your information, they will be able to decide if they can give you a prescription for HIV PrEP.

Any doctor or nurse practitioner in Alberta can give you a prescription for HIV PrEP. Alberta Health Services has a list of designated HIV PrEP prescribers who are specially trained and can prescribe HIV PrEP so that you get the medicine at no cost.

Taking HIV PrEP

HIV PrEP is taken as a pill 1 time every day.

When you take HIV PrEP, you will need to have regular appointments with your healthcare provider. You will also need to have blood tests and STI testing about 30 days after starting HIV PrEP, and every 3 months while you take it.

You can take HIV PrEP:

  • any time of day, with food or without food
  • with hormones, including birth control and hormone replacement therapy
  • with alcohol (since alcohol can make it harder to remember things, think about setting a phone alarm to remind you to take your medicine.)
  • Side effects

    The most common side effects of HIV PrEP include:

    • headache
    • stomach pain
    • weight loss
    • upset stomach (nausea) or vomiting
    • gas (flatulence)
    • loose stool (diarrhea)
    • dizziness

    Most of these side effects are mild and get better in a few weeks. If side effects bother you, change the time of day you take HIV PrEP or try taking it with food.

    In rare cases, HIV PrEP may cause damage to bone or kidneys. This damage tends to be mild and will get better after you stop HIV PrEP.

    HIV PrEP, STIs, and birth control

    HIV PrEP doesn’t prevent other STIs.

    It’s important to have regular STI testing and go for testing right away if you have symptoms of an STI, such as discharge from your penis or vagina, or burning when you pee (urinate).

    HIV PrEP doesn’t prevent pregnancy, so talk to your healthcare provider about birth control options.

    Learn more about STIs and birth control options.

    Stopping HIV PrEP

    If you want to stop taking HIV PrEP, wait 28 days after your last contact with someone who has HIV or who may have HIV.

    You should have HIV testing between 4 and 8 weeks after stopping HIV PrEP.

    More information

    For more information about HIV PrEP and sexual health, call Health Link at 811 or visit:

Current as of: September 13, 2023

Author: Provincial STI Program, Communicable Disease Control AHS