Yes, you can start and stop PrEP around periods when your risk goes up — like a vacation, a new relationship, or a stretch of casual dating — as long as you time it right and check in with a clinician. PrEP (pre-exposure prophylaxis) is daily HIV-prevention medicine taken before exposure. Stopping during low-risk gaps is reasonable, but it won't protect you the morning after.
risk reduction, taken as prescribed
daily Truvada/Descovy or the Apretude injection
not other STIs or pregnancy
| Item | Value |
|---|---|
| From sex | ~99% — risk reduction, taken as prescribed |
| From injection use | ≥74% |
| Forms | pill or shot — daily Truvada/Descovy or the Apretude injection |
| Protects against | HIV only — not other STIs or pregnancy |
What PrEP is and how it works
PrEP is medicine taken by HIV-negative people before a possible exposure to keep HIV from taking hold in the body CDC PrEP. It prevents infection rather than treating it. The active drugs build up in your blood and genital and rectal tissue so that if the virus shows up, it can't establish an infection. So "on and off" use depends on timing: you need enough drug in your system at the moment of exposure.
PrEP and PEP work differently. PrEP is taken on an ongoing basis before exposure. PEP (post-exposure prophylaxis) is the emergency option you start after a single possible exposure, and the two are not interchangeable CDC PEP. If you've already had a risky encounter and aren't on PrEP, start PEP quickly. A PrEP pill won't do the job.
How well it works
Taken as prescribed, PrEP reduces the risk of getting HIV from sex by about 99%. For people who inject drugs, it lowers risk by at least 74% when taken consistently. Those numbers assume the drug is actually in your system, and that's where seasonal use gets complicated.
Protection isn't instant. Time to maximum protection depends on the type of exposure: about 7 days of daily dosing for receptive anal sex, and about 21 days for receptive vaginal sex and for injection drug use. So if you're restarting PrEP before a trip or a new relationship, you have to start far enough ahead. Restarting the night before a vacation does almost nothing for vaginal-route protection and not much yet for anal.
How to use it and who it's for — the "on and off" question
There are two ways to take PrEP episodically. The first is the formal "2-1-1" or on-demand schedule, a specific event-driven regimen that some clinicians prescribe for certain men who have sex with men. It's its own protocol with strict timing, and you should only use it if a clinician has set it up with you. This guide is about the more common real-world pattern: people who go on daily PrEP for a season of higher risk (dating, a relationship change, travel) and come off during long low-risk gaps.
If that's you, restart daily dosing well before your risk window opens — counting back from those 7- or 21-day ramp-up times — and keep taking it daily through the whole window plus the days a clinician advises afterward. When you stop, do it on a plan, not by simply forgetting pills mid-season.
PrEP comes in a few forms, and which one fits depends on your situation:
- Truvada (daily pill): For people at risk through sex or through injection drug use.
- Descovy (daily pill): For people at risk through sex only — it's not for people assigned female at birth who are at risk through receptive vaginal sex.
- Apretude (cabotegravir injection): A shot for people at risk through sex who weigh at least 77 pounds (35 kg) — a good option if you'd rather not manage a daily pill.
One practical note on the injectable: a shot isn't built for casual stop-start use the way a pill is. If your risk comes and goes seasonally, a pill you can pause and restart on a plan is usually the more flexible tool.
What it's actually like to be on PrEP: you start with an HIV test to confirm you're negative, then have regular check-ins — repeat HIV testing, kidney monitoring, and STI screening — while you're on it. Clinics, primary-care offices, and telehealth services all prescribe it. Those check-ins are when an on-and-off plan gets sorted out, so don't skip them just because you're between risk periods.
Cost and how to get it
You can get PrEP from a primary-care doctor, a sexual-health clinic, or a telehealth service, and assistance programs exist to cover the cost for people who are uninsured or underinsured, so price shouldn't be the reason you go without. Starting always begins with that baseline HIV test. If you're planning to come on and off seasonally, tell whoever prescribes it; they can line up your restart timing and lab work around your calendar.
What PrEP does not protect against
PrEP guards against HIV and nothing else. It does not protect against other STIs — chlamydia, gonorrhea, and syphilis — and it does not prevent pregnancy. Being on PrEP can feel like full coverage, but you can still pick up gonorrhea or syphilis on PrEP, which is one reason regular STI testing stays on the schedule.
The other common mistake is treating PrEP like a morning-after pill. It only works when it's been taken on an ongoing schedule with enough lead time. Popping one after a risky night does not protect you. If a single exposure has already happened and you're not covered, that's a PEP situation.
How PrEP fits with the rest of your prevention
Think of PrEP as one layer. Condoms cover the gaps PrEP leaves — other STIs and pregnancy — and the two work better together than either alone; here's a fuller look at condoms vs prep. Vaccines (HPV, hepatitis B) add another layer for infections PrEP doesn't touch.
Regular testing is part of the package whether you're in an "on" season or not. Plan to get tested for HIV and other STIs at your PrEP check-ins, and if you've had a specific exposure, know when to test after exposure so your result actually means something. Prevention also works at the population level: when people living with HIV are diagnosed and treated, their risk of passing it on drops dramatically — more on how earlier hiv treatment can help prevention.
| PrEP | Condoms | |
|---|---|---|
| Prevents HIV | Yes (about 99% from sex when taken as prescribed) | Yes, when used correctly |
| Prevents other STIs | No | Yes |
| Prevents pregnancy | No | Yes |
| Good for on/off seasonal use | Yes, with a restart plan and lead time | Yes, use anytime |
When to talk to a clinician
Bring it up before any season of higher risk, not during it, since protection needs lead time to build. Talk to a clinician if you want to start, if you want to come off and might restart later, if your weight, kidney health, or pregnancy plans change, or if you've had an exposure and aren't sure whether you need PEP instead. A quick conversation turns "I'll take it when I need it" into an actual schedule that protects you.