PrEP ramp-up
When Am I Protected on PrEP?
Just started PrEP, or about to? Tell us your PrEP type and the kind of sex you have, and we'll pin down the exact day you're fully protected against HIV — and when you still need condoms in the meantime. Nothing you enter leaves your device.
This estimates when your PrEP reaches full protection against HIV. It never says you're "safe", and it can't replace the clinician who manages your PrEP — until you're fully protected, use condoms.
PrEP protection-onset calculator
This is general information based on CDC PrEP guidance, not a prescription, a diagnosis, or medical advice, and it doesn't replace the clinician who manages your PrEP. PrEP prevents HIV only — not other STIs. When in doubt about your protection, use condoms and ask your provider.
Start here
How PrEP protection builds up
PrEP doesn't switch on with the first pill. The medicine has to reach protective levels in the specific tissue exposed during sex, and different tissues get there at different speeds. That's why the two questions above — your regimen and the kind of sex — decide your protection date, not just the calendar.
For daily oral PrEP, the drug reaches protective levels in rectal tissue faster than in cervicovaginal tissue: roughly 7 days of consistent daily dosing for receptive anal sex, and about 20 days for receptive vaginal or front-hole sex. Consistency is the whole game — full protection depends on taking the pill every day.
Daily oral
About 7 days for anal sex, about 20 days for vaginal sex, with a pill every day. Descovy isn't approved for receptive vaginal sex — Truvada is.
On-demand 2-1-1
Per encounter, not a countdown: 2 pills 2–24h before sex, 1 pill at 24h, 1 pill at 48h. Validated for anal sex in people assigned male only.
Injectable
Cabotegravir shot; a firm days-to-protection isn't established. Many clinicians advise condom backup for about the first week — confirm with your provider.
The gap that matters
Until you reach full protection, use condoms
The window between your first dose and full protection is real, and it's exactly when it's easy to assume you're already covered. During the ramp-up, a condom is what closes the gap. Once your regimen reaches full protection, PrEP is highly effective at preventing HIV — but only HIV.
PrEP does nothing for chlamydia, gonorrhea, syphilis, herpes, or other STIs. That's not a limitation of your particular pill or shot; it's what PrEP is. Regular STI testing stays part of staying healthy on PrEP, which is also why your prescriber rechecks you at each visit. If you think you've already been exposed to HIV and you're not yet protected, that's a PEP question — a time-critical emergency course — not a PrEP one.
Next steps
Get the rest of your PrEP plan sorted
Am I a candidate for PrEP?
A quick check of whether PrEP is recommended for your situation.
Which PrEP is right for me?
Daily pill, on-demand 2-1-1, or the shot — compare what fits your life.
Do I need PEP?
Already exposed and not yet protected? PEP is time-critical — check now.
What will PrEP cost me?
Insurance, copay programs and free options that can bring PrEP to $0.
Sources
Where this guidance comes from
The time-to-protection estimates, the 2-1-1 dosing schedule and who it's validated for, and the injectable-onset guidance are read from the CDC's PrEP overview and its 2021 clinical practice guideline. We follow those; we don't reinterpret them, and where the evidence is uncertain — as with injectable onset — we say so.
Medically Reviewed & Fact-Checked · Updated
Reviewed by EasySTD Editorial Team
Compiled and checked by EasySTD's editorial team against CDC and public-health sources. This is educational information, not a substitute for advice from a licensed clinician. Our editorial guidelines →
2 Sources
Data & references
- CDC: Pre-Exposure Prophylaxis (PrEP)https://www.cdc.gov/hiv/risk/prep/
- CDC: Preexposure Prophylaxis for the Prevention of HIV Infection — Clinical Practice Guideline, 2021https://www.cdc.gov/hiv/pdf/risk/prep/cdc-hiv-prep-guidelines-2021.pdf
EasySTD is an information and comparison directory, not a healthcare provider. This tool is general information based on published PrEP guidance: it is not medical advice, a prescription, or a diagnosis, and it does not create a doctor-patient relationship. It cannot manage your PrEP or tell you your individual risk. Confirm your protection timing and dosing with the clinician who prescribed your PrEP.
Good to Know
Protection on PrEP: frequently asked questions
When each regimen kicks in, how anal and vaginal sex differ, and why condoms still matter.
How long until I'm protected on daily PrEP?
On daily oral PrEP, protection builds up over the first days and weeks of consistent dosing. CDC guidance indicates PrEP reaches maximum protection for receptive anal sex at about 7 days of daily use, and for receptive vaginal sex at about 20 days (up to roughly 21). It is not protective from the very first pill, which is why condoms matter during the ramp-up. Taking your pill every day is what gets you there and keeps you there.
Does the time-to-protection differ for anal versus vaginal sex?
Yes. The drug reaches protective levels in rectal tissue faster than in cervicovaginal tissue, so daily PrEP is estimated to reach full protection at about 7 days for receptive anal sex but about 20 days for receptive vaginal or front-hole sex. Also note that Descovy (TAF/FTC) is not FDA-approved for people having receptive vaginal sex — Truvada (TDF/FTC) is the option studied for that route — so confirm which pill you're on if vaginal sex is part of the picture.
What is 2-1-1 (on-demand) PrEP and who is it for?
2-1-1, also called on-demand or event-driven PrEP, means taking 2 pills 2–24 hours before sex, then 1 pill 24 hours after the first dose, and 1 more pill 48 hours after the first dose. It's protective for that planned encounter once the initial double dose is on board. Importantly, 2-1-1 has only been validated for anal sex in people assigned male at birth. It is not recommended for receptive vaginal or front-hole sex — for that, daily PrEP is the route with evidence behind it.
When am I protected after the PrEP shot (cabotegravir / Apretude)?
A precise number of days to full protection after the first injection isn't firmly established the way it is for daily pills. Because of that, many clinicians advise using condoms as backup for roughly the first 7 days after your first shot and confirming the timing with the provider who gave it. The injection schedule is a second shot one month after the first, then one every two months. Don't rely on a hard self-calculated date — confirm onset and your next appointment with your provider.
Do I still need condoms once I'm on PrEP?
During the ramp-up period — before your regimen reaches full protection — yes, use condoms. And even after you're fully protected, remember PrEP prevents HIV only. It does not protect against other STIs such as chlamydia, gonorrhea, syphilis, or herpes, so condoms plus regular STI testing still have a role. PrEP is one layer of protection, not the whole picture.
Is what I enter into this calculator private?
Yes. This tool runs entirely in your browser. Your regimen, the kind of sex you have, and your start date are never sent to a server, saved, or shared — nothing leaves your device. Close the tab and it's gone. It's general information based on CDC PrEP guidance; it isn't a prescription, a diagnosis, or a substitute for the clinician who manages your PrEP.
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