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PrEP side effects & interactions

All Freddie patients are regularly tested for side effects from PrEP. Book a free phone consultation to learn more.


PrEP Side Effects 101

Less than 10% of patients experience any PrEP side effects. Most go away within 1-2 weeks.

Potential short-term side effects include nausea, headaches, diarrhea, and vomiting.

Potential long-term side effects are rare and usually reversible after stopping PrEP.

Regular testing while on PrEP is mandatory to monitor HIV status & PrEP tolerance

Freddie is Canada’s largest PrEP clinic, and now available in the US. Freddie patients have a choice between PrEP medications and access to email & phone support for all their PrEP questions.

What is PrEP?

PrEP (pre-exposure prophylaxis) is a daily HIV prevention pill that reduces the risk of contracting HIV by up to 99%. If you take a PrEP prescription daily, the medicine in your bloodstream helps stop HIV from replicating in your body, ensuring you remain HIV-negative.

What are the different types of PrEP?

While PrEP is the type of medication, there are two formulas currently available in the US: Truvada & Descovy. Both are 99% effective at preventing HIV. The primary differences between the two pills are:

Both PrEP formulas are safe for most patients. Though, Descovy has even fewer reported side effects.

Patients with pre-existing conditions are more likely to be able to access PrEP by taking Descovy.

Truvada has a generic version available, making it more cost-affordable for patients without private isurance.

PrEP 101

PrEP is a daily pill that is 99% effective at preventing the transmission of HIV.

PrEP is approved in Canada and requires a prescription. The two forms of PrEP are Truvada & Descovy.

Only 1-10% of patients on PrEP experience side effects. Most symptoms tend to go away within 1-2 weeks naturally.

PrEP only protects against HIV, not other sexually transmitted infections (STIs) like syphilis, gonorrhea, chlamydia, or hepatitis.

The vast majority of Freddie patients get PrEP prescribed online & discreetly delivered for $0.

Who is PrEP for?

PrEP can be taken by anyone that is HIV-negative and looking for additional protection against HIV. This includes men who have sex with men, transgender women, and gender-diverse communities.

If you are considering PrEP, it’s recommended you chat with your PrEP provider to determine which method best fits your needs.

Our clinicians are inclusive and have worked with 22,000+ patients. They’re happy to address any questions or concerns you have for free!

PrEP Side Effects

Short-term side effects of PrEP

Some of the possible short-term side effects associated with PrEP include nausea, headaches, diarrhea, and vomiting.

Trials show that these side effects impact between 1% and 10% of people on PrEP and that they are generally mild and clear up on their own within a week or two.

Please get in touch with your healthcare provider if you’re experiencing persistent symptoms after a couple of weeks.

Long-term side effects of PrEP

In a small number of people, PrEP has resulted in a decrease in kidney 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.

Attending the mandatory lab testing every three months while on PrEP is how you and your PrEP provider can be sure that PrEP is being tolerated well and not negatively impacting your health.

Testing for side effects of PrEP

Kidney function is tested before starting PrEP and with the regular lab work performed while taking PrEP. This includes blood and, as needed, urine testing.

Freddie and scientific literature recommends taking Vitamin D with PrEP to ensure optimal bone health.

If you have a significant risk of bone issues from other health issues and are taking Truvada or its generic version, your Freddie clinician will talk with you and your primary care provider (if available) about how to ensure you maintain the best possible bone health.

How to reduce side effects from PrEP

PrEP + other drugs

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

It is important to inform your clinician about any medications, supplements, or recreational drugs you are taking to ensure that any potential drug interactions are considered before going on PrEP.

PrEP + Medication

Of the drugs and supplements that interact with PrEP, non-steroidal anti-inflammatory drugs (NSAID) are the most commonly used and should be avoided if possible.

These are usually found in pain-relief medication, so remember the following:


Acetaminophen (brand name Tylenol)

Don’t take regularly (if possible):

Ibuprofen (brand name Advil)

Acetylsalicylic acid (brand name Aspirin)

Naproxen (brand name Aleve)

The above-listed medications are all NSAIDs and can cause kidney damage if taken in high amounts or for long periods. When combined with PrEP, regular use of NSAIDs increases the risk of kidney damage from both medications.

PrEP + Recreational drugs

PrEP is considered safe for those who use recreational drugs or share drug injection equipment. Canada’s PrEP guidelines recommend PrEP for these individuals.

Studies demonstrate that PrEP does work to prevent HIV for people who inject drugs when adherence is high. Although the vast majority of PrEP studies have looked at preventing sexual HIV transmission, one major PrEP study was done with people who inject drugs. The Bangkok Tenofovir Study found an 84% reduced risk of getting HIV among people who injected drugs and were highly adherent to daily PrEP. Although this level of protection is not as high as some other PrEP studies, one possible explanation is that it only considered one PrEP component, TDF (rather than TDF + FTC), which is not the standard of care for oral PrEP.

It is important to note that combination prevention, using multiple HIV prevention strategies simultaneously, can decrease one’s risk of getting HIV. So, PrEP, condoms, HIV treatment, STI testing, needle distribution programs, and other harm reduction methods can provide a more effective and complete prevention strategy.

We’ve walked thousands of patients through the PrEP process for free, and we’re ready to do the same for you! Book a free consultation with an inclusive clinician today!


People of all genders can use PrEP, as PrEP components do not interact with hormones some trans people choose to 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 in the body by a small amount, although drug levels still remain high enough to protect against HIV.

Trans men and trans women are recommended to take daily PrEP rather than PrEP on-demand to maximize their protection.

There is no reason to believe that PrEP is not highly effective when taken consistently and correctly by trans men. As with anyone on PrEP, the drug must reach sufficient concentrations before it’s effective in preventing HIV. That does not necessarily rely on your gender but instead on what kind of sex you’re having. The drugs in PrEP take about 21 days to reach maximum levels in vaginal tissues compared to 7 days for rectal tissues.

Studies on the effectiveness of PrEP in trans men are underway.
Due to ongoing transphobia and trans erasure, this population has been excluded from studies of PrEP effectiveness to date. When it comes to HIV risk, anyone who has sex with men who have sex with men (i.e. gay, bisexual, and queer men) may be at higher HIV risk.

PrEP + pregnancy

Most commonly useIf 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 for chestfeeding.

Although there have not been any clinical trials specifically evaluating the efficacy and safety of PrEP during pregnancy, multiple studies in various cisgender populations have shown that the consistent, correct use of oral PrEP is highly effective in preventing HIV transmission.

Thousands of pregnant cisgender women living with HIV have used the drugs (TDF and FTC) found in PrEP as part of their treatment. Research on pregnant cisgender women using TDF in treating hepatitis B has found that these medications are generally safe for these women and fetal development.d medications and recreational drugs are not known to interact with PrEP, but there are some.

Studies have shown no increased risk of birth defects, preterm delivery, or low birth weight associated with using TDF during pregnancy and lactation.

However, limited evidence has found that infants born of mothers on TDF may have lower bone density.

Despite data suggesting that PrEP is safe to take during pregnancy and chestfeeding, it is important to attend regular clinical follow-ups to monitor the mother and infant's health.

Is PrEP safe?

Yes, PrEP is considered safe for the vast majority of people that take the medication. More people are taking PrEP every year, and the global number is nearing 1,000,000 reported patients.

When discussing the safety of PrEP, it’s helpful to remember:

Only 1-10% of patients experience mild side effects, which usually go away within two weeks.

Side effects from PrEP are tested for; if discovered, most are reversible after stopping PrEP.

Descovy is a new form of PrEP that is safe for those with pre-existing conditions.

Book a free consultation to talk to a licensed medical professional today.


How long do side effects last for PrEP?
Is PrEP effective after three days?
Is weight gain a side effect of PrEP?
Are there side effects to stopping PrEP?
What happens if you skip a day on PrEP?
Can PrEP damage your kidneys?
Who should not use PrEP?
How long until PrEP is out of your system?
What can cause PrEP to fail?

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