Had a possible HIV exposure in the last 72 hours while you weren't sure you were protected? Don't wait for your next refill or appointment. PEP (post-exposure prophylaxis) works best the sooner it starts and must begin within 72 hours. Here's how to get PEP fast.
Missed a daily PrEP pill
This covers generic Truvada (F/TDF), Truvada and Descovy (F/TAF) taken once a day. CDC's patient medication guide gives the basic rule:
- Take the missed pill as soon as you remember.
- If your next dose is almost due, skip the missed one and take the next pill at your usual time.
- Never take a double dose to make up for the one you missed.
- Get back on your normal schedule the next day.
The same CDC guide says an occasional missed dose won't greatly affect PrEP's overall effectiveness. Missing several doses, or stopping, does raise your risk.
Why the kind of sex you have matters
How forgiving PrEP is of missed pills depends on the kind of exposure. CDC's clinical guideline notes that with daily pills, drug levels peak in rectal tissue after about 7 days but take about 20 days in cervical and vaginal tissue. That slower build-up is also why pill-taking studies in cisgender women found protection depended more heavily on near-daily dosing. If your risk comes from vaginal or front-hole sex, or from injecting drugs, consistent daily dosing matters more.
If you've missed several days in a row
CDC's 2021 clinical guideline says protection from daily oral PrEP fades over roughly 7 to 10 days after you stop taking it. If you've had a gap of more than a few days:
- Possible exposure in the last 72 hours? Contact a clinician about PEP before anything else.
- No recent exposure? Call your prescriber before restarting. Restarting after a real break usually means a fresh HIV test first, because starting PrEP with undiagnosed HIV can lead to drug resistance.
- Have hepatitis B? Tell your prescriber about any gap. Stopping and starting tenofovir-based PrEP can cause hepatitis B flares.
If you use the on-demand 2-1-1 schedule rather than daily pills, the rules are different. Ask your prescriber how your schedule handles a missed dose, and see our oral vs injectable comparison for how the options differ.
Late for an Apretude (cabotegravir) shot
Apretude is injected every 2 months after two starting injections given one month apart. According to the prescribing information summarized by the National HIV PrEP Curriculum, a shot can be given up to 7 days before or after its target date. Past that, it depends on which shot you missed and how long it's been:
| Missed shot | Time since your last shot | What the label says |
|---|---|---|
| Second starting shot | 2 months or less since the first | Give it as soon as possible, then continue every 2 months |
| Second starting shot | More than 2 months | Restart: one shot, then another one month later |
| Third or later shot | 3 months or less | Give it as soon as possible, then continue every 2 months |
| Third or later shot | More than 3 months | Restart with two starting shots one month apart |
If you know ahead of time you'll miss a shot by more than 7 days, for example because of travel or surgery, the label allows daily oral cabotegravir tablets for up to 2 months to bridge the gap. Ask about this before the gap, not after.
Your clinic will also want a fresh HIV test before the late shot. The label calls for HIV testing before every Apretude injection.
Late for a Yeztugo (lenacapavir) shot
Yeztugo is injected every 26 weeks (about every 6 months). CDC's 2025 clinical recommendation sets a window of 2 weeks either side of that date.
- Planned delay of more than 2 weeks: the label allows weekly oral lenacapavir tablets as a bridge for up to 6 months. CDC says injections should start again within 7 days after the last tablet.
- Unplanned delay of more than 2 weeks, with no bridging tablets: CDC says your clinician should talk with you about what happened, decide whether to restart, and restart with the full starting doses if so. The label says that once more than 28 weeks have passed since the last injection, you restart from day 1.
As with Apretude, you'll get an HIV test before the shot. Yeztugo's boxed warning requires HIV testing before starting and before every injection. Our Yeztugo vs. Apretude comparison covers the schedules side by side.
The "tail" doesn't protect you. Both injectables stay in your body at slowly falling levels for months after a missed shot. Those levels can be too low to prevent HIV but still high enough to let drug-resistant virus develop if you get HIV. Being late isn't something to sit on. Call your clinic as soon as you know.
When to ask about PEP
PEP is a 28-day course of HIV medicine started within 72 hours of a possible exposure. Ask about it if all three of these are true:
- You missed enough PrEP that you may not have been protected (several days of daily pills, or an injection well past its window),
- you had condomless sex or shared injection equipment with someone whose HIV status you don't know or who has a detectable viral load, and
- it was within the last 72 hours.
Emergency rooms, urgent care and some telehealth services can start PEP. The sooner PEP starts, the better it works.
How to miss fewer doses
- Tie the pill to a daily habit like brushing your teeth or your morning coffee, and keep the bottle where you'll see it.
- Use a weekly pill organizer so you can see at a glance whether you took today's dose.
- Carry a spare dose in your bag or car for nights away from home.
- Put injection dates in your calendar as soon as you get each shot, with a reminder two weeks before.
- Consider a different option. If daily pills keep slipping, that's a common, legitimate reason to switch to injectable PrEP.
For what the first few weeks on daily pills feel like, see your first month on PrEP. Whatever you're on, an HIV test is the first step back. Our sister site explains which HIV test types catch infection earliest.
Frequently Asked Questions
I missed one PrEP pill. Am I still protected?
Can I take two PrEP pills to make up for a missed one?
How late can my Apretude shot be?
How late can my Yeztugo shot be?
When should I get PEP instead?
Sources
- CDC Let's Stop HIV Together: PrEP medication guide for patients (PDF)
- National HIV PrEP Curriculum (University of Washington): Apretude prescribing information summary, missed-injection table
- CDC MMWR: Clinical Recommendation for the Use of Injectable Lenacapavir as HIV PrEP, United States, 2025
- Yeztugo U.S. prescribing information (Gilead Sciences)
- CDC/USPHS: Preexposure Prophylaxis for the Prevention of HIV Infection in the United States, 2021 Update (clinical practice guideline)
This guide is general health information, not medical advice, and it doesn't replace a conversation with a clinician who knows your history. Guidance and program rules change; we last reviewed this page on October 12, 2026. Spot something out of date? Tell us.