My PrEP
What it is
Post-exposure prophylaxis with an antibiotic: a dose taken after the risk, before an infection has time to establish itself.
One dose, after the fact
doxyPEP — doxycycline post-exposure prophylaxis — is a single 200 mg dose of doxycycline taken after sex without a condom. Doxycycline is a tetracycline antibiotic that has been prescribed for decades, cheaply, for acne, chest infections, malaria prevention and STI treatment; here it is used at the moment bacteria are trying to settle in.
What it does
It works against the three bacterial STIs — syphilis, chlamydia and gonorrhoea — with very different success. Syphilis and chlamydia are highly sensitive to it. Gonorrhoea often is not, because tetracycline-resistant strains are common in many places, so the protection there is partial at best.
What it does not do
Nothing against HIV, herpes, HPV, hepatitis B or C, or mpox — those are viruses, and doxycycline is an antibiotic. It is not a contraceptive. It replaces neither PrEP nor condoms nor vaccination nor regular testing; every guideline frames it as one more tool alongside them.
Who it is for
A deliberately narrow group: people with a high rate of bacterial STIs, for whom the benefit clearly outweighs the resistance cost.
The trials that proved doxyPEP works were run in men who have sex with men and transgender women who already had a high rate of bacterial STIs — and every national guideline has kept to that population. The exact threshold varies by country (see the section on where you live), but the shape is the same:
Guidance does not recommend doxyPEP for cisgender women, and most bodies extend that to trans men and to men who only have sex with women. The reason is evidence, not judgement: the one large trial in cisgender women (Kenya, 2023) found no reduction in STIs — most likely because few participants actually took the tablets — and there is no data at all in the other groups. The UK leaves the door open case by case for people assigned female at birth; France closes it explicitly.
How to take it
200 mg, as soon as possible after sex, at most 72 hours later — and never more than one dose per 24 hours.
- As soon as possibleTake 200 mg (2 × 100 mg) with a large glass of water, ideally with food.
- Within 24 hoursThe window every guideline aims for.
- Up to 72 hoursStill worth taking. Beyond that, no benefit — wait for the next exposure.
Doxycycline acts while the bacteria are still multiplying at the point of entry. The earlier the dose, the better; 72 hours is a maximum, not a target.
The rules that go with the dose:
What we know about how well it works
Excellent against syphilis and chlamydia, unreliable against gonorrhoea, unproven in women.
Across the two positive trials, people on doxyPEP had roughly two-thirds fewer bacterial STIs overall, and the effect was strikingly consistent for syphilis and chlamydia. Gonorrhoea is the exception, and it is not a matter of the tablet failing: gonococci in many cities already carry tetracycline resistance, so there is less for the drug to act on. The Kenyan trial in women is best read as an adherence result — most participants had no detectable drug — but it means the benefit in women is simply not demonstrated, which is why guidance stops short of recommending it there.
The resistance question
This is what makes doxyPEP different from PrEP: the cost is collective. Every dose selects for resistant bacteria — in the STIs it targets and in the ones you carry every day.
Gonorrhoea is already escaping
Where doxyPEP has been used widely, gonorrhoea has adapted fast: in Seattle, the share of strains with high-level tetracycline resistance went from a few percent to around two-thirds between 2021 and 2024, and a 2026 study in southern California measured a rapid loss of protection against gonorrhoea after roll-out. Syphilis and chlamydia have not shown resistance so far — but sustained pressure could change that.
Bystander bacteria
Doxycycline does not know which bacteria it is meant for. In the trials, users carried more tetracycline-resistant Staphylococcus aureus in the nose and more resistance genes in the gut. Nobody knows yet what that means for treating a future skin, chest or urinary infection — which is exactly why guidance is cautious.
Why the target is narrow
For someone getting several bacterial STIs a year, the personal benefit is large and the extra antibiotic exposure is modest compared with the treatment courses avoided. For someone rarely exposed, the equation flips. Every guideline draws its line at that trade-off, and asks that it be revisited regularly.
Side effects and precautions
Mostly stomach upset and sun sensitivity, both easy to limit; a short list of people who should not take it.
The follow-up that goes with it
Regular STI testing is not optional here: it is how a partial protection stays honest.
Because doxyPEP is unreliable against gonorrhoea, an infection you don't test for is an infection you keep passing on. Three-monthly testing is the same rhythm as HIV PrEP follow-up, and most people on both have it done in one visit. Contacts of syphilis who consistently take doxyPEP may, in the UK, choose testing over presumptive treatment — a detail worth raising with your clinic rather than deciding alone.
What your country recommends
doxyPEP is off-label everywhere. What differs is the position of the national body, who it names, and where you can actually get it — this is the part to check for where you live.
In the United Kingdom, BASHH formally recommends doxyPEP for a defined group (9 June 2025), as one component of STI prevention alongside testing, vaccination and condoms.
The group named: cisgender gay, bisexual and other men who have sex with men, and transgender women, at elevated risk of acquiring syphilis — in practice, a bacterial STI or several partners in the past year.
For people assigned female at birth at elevated risk of syphilis, clinicians may consider it case by case, in discussion with the person.
The guidance is framed as prevention of syphilis — and by extension chlamydia — and states plainly that doxyPEP is unlikely to prevent gonorrhoea.
It is prescribed and dispensed free of charge through sexual health clinics.
In the United States, the CDC formally recommends doxyPEP for a defined group (June 6, 2024), as one component of STI prevention alongside testing, vaccination and condoms.
The group named: men who have sex with men and transgender women who have had at least one bacterial STI — syphilis, chlamydia or gonorrhoea — in the past 12 months.
No recommendation is made for cisgender women, for lack of evidence of benefit.
The guidance covers the three bacterial STIs, with the usual caveat that protection against gonorrhoea is partial.
It is a prescription generally covered by insurance; some pharmacies and sexual health programmes dispense it directly.
In Ireland, there is no national guideline yet. The HSE has issued interim or regional guidance (2025), and some services already offer doxyPEP to people at high risk of bacterial STIs — the answer depends on where in the country you are.
The group named: cisgender gay, bisexual and other men who have sex with men, and transgender women, at elevated risk of acquiring syphilis — in practice, a bacterial STI or several partners in the past year.
The guidance is framed as prevention of syphilis — and by extension chlamydia — and states plainly that doxyPEP is unlikely to prevent gonorrhoea.
Some sexual health services provide it; ask the clinic that follows you.
In Canada, there is no national guideline yet. The BCCDC has issued interim or regional guidance (October 27, 2023), and some services already offer doxyPEP to people at high risk of bacterial STIs — the answer depends on where in the country you are.
The group named: gay, bisexual and other men who have sex with men, and transgender women, with a bacterial STI in the past year.
The guidance covers the three bacterial STIs, with the usual caveat that protection against gonorrhoea is partial.
Some sexual health services provide it; ask the clinic that follows you.
Where you live, we could not find a national position on doxyPEP. Across Europe, most countries have not taken one yet and are waiting on WHO and ECDC; individual sexual health clinics may still discuss it with you.
Where to go, who to talk to
Local resources to get tested, start PrEP or ask questions — confidential.
- NHS — Find a sexual health clinicFind where to get a test or PrEP near you.
- THT Direct — Terrence Higgins Trust0808 802 1221 · Mon–Fri, 10am–6pmInformation and support line, confidential.
- NHS — Pre-exposure prophylaxis (PrEP)Trusted reference information and organisations.
- CDC GetTested — testing & prevention locatorFind where to get a test or PrEP near you.
- HIV.gov — national hotline (CDC-INFO)1-800-232-4636 · Mon–Fri, 8am–8pm ETInformation and support line, confidential.
- HIV.gov — Pre-Exposure Prophylaxis (PrEP)Trusted reference information and organisations.
- HSE — Sexual health services and clinicsFind where to get a test or PrEP near you.
- HSE — HIV and Sexual Health Helpline1800 459 459 · Mon–Fri, 9.30am–5.30pmInformation and support line, confidential.
- HIV Ireland — PrEPTrusted reference information and organisations.
- CATIE — Where To? (service finder)Find where to get a test or PrEP near you.
- Action Canada — Access Line1-888-642-2725 · Every day, 9am–9pm ETInformation and support line, confidential.
- CATIE — HIV pre-exposure prophylaxis (PrEP)Trusted reference information and organisations.
- PrEPWatch — global PrEP availability (AVAC)Find where to get a test or PrEP near you.
- aidsmap — HIV information (PrEP)Trusted reference information and organisations.
Frequently asked questions
The questions people ask before their first dose.
One dose per partner, or one per night?
One per 24-hour window, whatever happens inside it. Three partners in one evening is still one dose. If sex continues the next day, that is a new day and a new dose — at least 24 hours after the last one.
Should I wait until the end of a weekend and take one dose?
No. Take the first dose as soon as possible after the first exposure — protection is best in the first 24 hours — then one dose per day while exposures continue. UK guidance does allow one dose at the end of a 72-hour period of repeated sex as a fallback, but earlier is better.
Does it replace PrEP or condoms?
No. doxyPEP does nothing against HIV, and nothing against herpes, HPV, hepatitis or mpox. HIV PrEP prevents HIV, condoms reduce all of these, vaccines cover hepatitis A and B, HPV and mpox. doxyPEP adds protection against syphilis and chlamydia on top; that is all it claims.
Can I take it with PrEP?
Yes. There is no interaction with oral or injectable HIV PrEP, and the follow-up visits — STI testing every three months — are the same, so most clinics manage both together.
How many doses can I take a week?
Never more than one per 24 hours, everywhere. Some countries add a ceiling: France caps it at three doses a week; the US guidance sets no weekly limit but stresses that heavy use increases the resistance pressure. Your country's rule is in the section above.
I'm a woman — is it for me?
Current guidance does not recommend it, because the one large trial in cisgender women found no benefit — most likely an adherence problem, but a benefit that was never shown cannot be promised. The UK allows clinicians to consider it case by case for people assigned female at birth at high risk of syphilis. It is a conversation to have, not a door that is closed forever.
Why do some countries recommend it and others not?
Because they weigh the same evidence differently: strong personal benefit against syphilis and chlamydia on one side, resistance in gonorrhoea and in everyday bacteria on the other. Countries with rising syphilis and good surveillance have moved first; several European countries are waiting for WHO and ECDC positions. The evidence is the same everywhere; the risk appetite is not.