What not to do while on PrEP?: A guide to medication adherence and safe practices

October 7, 2025 •

4 min read

PrEP is over 99% effective at preventing HIV from sex when taken consistently as prescribed. Knowing what not to do while on PrEP, such as missing doses or ignoring drug interactions, is crucial for maintaining this high level of protection and ensuring overall health.

Quick Summary

This guide provides essential information on practices and substance use to avoid while taking PrEP. It highlights the importance of medication consistency, outlines potentially harmful drug interactions, clarifies the limits of PrEP protection, and emphasizes the need for regular medical follow-ups.

Key Points

Do not miss doses: Consistent daily or scheduled PrEP use is crucial to maintain protective drug levels. Inconsistent use significantly lowers effectiveness.
Avoid interacting medications: Regular, high-dose NSAID use and some Hepatitis C drugs can interact with PrEP; always inform your doctor about all medications and supplements.
Stay on top of testing: Do not neglect regular HIV and STI testing, as PrEP requires an HIV-negative status and does not protect against other STIs.
Be mindful of substance use: While alcohol and recreational drugs don't directly interact with PrEP, they can disrupt routine and increase the risk of missing doses.
Do not abandon safe sex practices: PrEP is not a substitute for condoms, which remain essential for protecting against other sexually transmitted infections.
Do not ignore side effects: While common side effects are usually mild, persistent or severe symptoms should be discussed with your healthcare provider.
Never share your PrEP medication: Your prescription is tailored to you based on your health status and needs; sharing medication is unsafe and potentially illegal.

For anyone taking Pre-Exposure Prophylaxis (PrEP), adherence to the prescribed regimen is paramount for its effectiveness. While PrEP is a powerful tool in HIV prevention, certain actions and practices can undermine its protective benefits. Understanding the critical 'don'ts' is just as important as knowing the 'dos'.

Failing to take PrEP consistently

This is the single most significant mistake a person can make while on PrEP. For oral PrEP to be effective, it must build up a protective level of medication in the body, which requires consistent, daily dosing. Missing doses, especially multiple doses in a row, can cause drug levels to drop, reducing or eliminating protection against HIV.

What happens when you miss a dose?

Single missed dose: If you forget a single daily oral dose, take it as soon as you remember. If it's closer to your next scheduled dose, skip the missed one and continue your regular schedule. Do not double up on doses, as this can increase side effects. For injectable PrEP, missing an appointment is more serious and requires immediate contact with your healthcare provider.
Multiple missed doses: Missing several doses significantly jeopardizes your protection. According to the CDC, if you miss more than a week of pills, you will need to re-establish adequate drug levels in your body, which can take up to seven additional daily doses. If you have been inconsistent, it is vital to speak with your doctor to re-evaluate your protection status.

Mixing PrEP with specific medications and supplements

Certain substances can interact with PrEP medications, affecting kidney function or the drug's effectiveness. Always inform your doctor or pharmacist about all medications, supplements, and herbal remedies you are taking.

Common medications and supplements to monitor:

NSAIDs: Regular or high-dose use of non-steroidal anti-inflammatory drugs like ibuprofen (Advil, Motrin), naproxen (Aleve), or diclofenac can affect your kidneys. Since some oral PrEP forms (like Truvada) are processed through the kidneys, regular use of NSAIDs may increase the risk of kidney problems. Occasional use is generally safe, but chronic use should be discussed with a doctor.
Hepatitis C medications: Some drugs used to treat Hepatitis C, such as sofosbuvir and ledipasvir, can interact with PrEP. It is essential to tell your doctor if you are receiving treatment for Hepatitis C.
Creatine supplements: Used by many for fitness, creatine can affect the results of kidney function tests. This may cause a test to inaccurately show that your kidneys are not functioning normally, which could impact whether your doctor feels it is safe for you to continue PrEP.
Herbal supplements: Products like St. John's Wort can interact with medications and should be discussed with your healthcare provider. The safety of combining many herbal remedies with PrEP is not well-documented.

Neglecting regular HIV and STI testing

One of the most dangerous mistakes is assuming PrEP eliminates the need for ongoing medical care. PrEP is a prevention tool for HIV-negative individuals. Taking PrEP while unknowingly having HIV can lead to drug-resistant strains of the virus.

A note on testing:

You must test negative for HIV immediately before starting PrEP.
The CDC recommends retesting for HIV at least every three months while on PrEP.
Regular testing for other STIs is also crucial, as PrEP does not protect against them.

Misusing alcohol and recreational drugs

While alcohol does not directly impact PrEP's effectiveness, excessive consumption can lead to lapses in judgment and poor adherence to your dosing schedule. Similarly, recreational drug use, particularly if it disrupts your routine, can increase the chances of missing a dose. It is important to remember that substance use does not make PrEP ineffective, but it can make you inconsistent with your medication, which is what compromises protection.

Believing PrEP protects against other STIs

PrEP is specifically for preventing HIV transmission. It does not protect against other sexually transmitted infections like gonorrhea, chlamydia, or syphilis. Relying on PrEP alone and abandoning other safer sex practices, such as condom use, can increase your risk for these other infections. Condoms used alongside PrEP offer the highest level of protection against both HIV and other STIs.

Comparison of risks for PrEP users


Action	Risk to PrEP Efficacy	Other Health Risks	Recommendation
Missing doses inconsistently	High risk of reduced protection and potential HIV seroconversion	None directly related to the missed dose itself, but inconsistent drug levels are suboptimal	Take consistently. Use reminders. See doctor if you struggle.
Regularly taking NSAIDs (e.g., ibuprofen)	Minimal or no effect on PrEP efficacy	Potential for kidney problems, especially with older-generation PrEP (Truvada)	Discuss regular use with your doctor; consider acetaminophen for pain relief.
Ignoring regular HIV testing	Moderate to high risk. Can develop HIV resistance if unknowingly positive	Undetected HIV infection, potential for delayed treatment and progression	Follow CDC guidelines for quarterly testing to confirm status.
Excessive alcohol/drug use	High risk due to potential missed doses from impaired routine	Impaired judgment leading to riskier behavior; general health concerns	Be mindful of routine and take medication consistently, even during substance use.
Discontinuing condoms	No risk to PrEP efficacy, but greatly increases risk for other STIs	Risk of gonorrhea, chlamydia, syphilis, hepatitis B, etc.	Continue using condoms consistently in addition to PrEP for comprehensive protection.

Conclusion

PrEP is a highly effective tool for HIV prevention, but its success relies on consistent adherence and responsible health practices. Avoid major missteps such as missing doses, disregarding potential drug interactions, neglecting regular medical check-ups, or discontinuing other safer sex practices. By being proactive and transparent with your healthcare provider, you can ensure your PrEP regimen offers maximum protection while safeguarding your overall health. For additional resources and guidelines, consider visiting the official CDC HIV Nexus website.

Frequently Asked Questions

If you remember within 12 hours of your usual time, take it immediately. If it's been more than 12 hours, skip the missed dose and take your next pill at the usual time. Do not double up to make up for a missed dose.

Occasional use of NSAIDs like ibuprofen is generally fine. However, regular, high-dose use of NSAIDs can affect your kidneys, so discuss this with your doctor, especially if you are on older PrEP formulations like Truvada.

No, PrEP only prevents HIV. It does not protect against other STIs such as gonorrhea, chlamydia, syphilis, or herpes. Condoms should still be used to prevent the transmission of other STIs.

Yes, there is no direct interaction between PrEP and alcohol. However, excessive drinking can impair your judgment and affect your ability to take your medication consistently, which would compromise your protection.

The Centers for Disease Control and Prevention (CDC) recommends that you get tested for HIV and other STIs at least every three months while on PrEP.

If you test positive for HIV, you should stop taking PrEP immediately and contact your doctor. PrEP is not for treatment, and continuing it could lead to drug-resistant HIV strains.

While creatine does not directly interact with PrEP, it can alter the results of kidney function tests. Always inform your doctor about your creatine use so they can accurately interpret your test results.