My PrEP
What it is
Two antiretrovirals in one tablet, keeping enough drug in the blood and mucous membranes to block HIV at the point of entry.
Two molecules in one tablet
PrEP — pre-exposure prophylaxis — is a medicine taken by an HIV-negative person to avoid contracting HIV. Oral PrEP combines tenofovir disoproxil and emtricitabine, and is widely available as a generic.
What the medicine does
It keeps enough drug in the blood and mucous membranes to block the virus as it enters, before it can multiply. It is not a vaccine: protection exists only while the drug is there, which is why how you take it matters as much as the tablet itself.
It only protects against HIV
It has no effect on other sexually transmitted infections — chlamydia, gonorrhoea, syphilis, hepatitis, mpox — nor on pregnancy. Condoms, vaccination and regular screening all keep their place.
Who it is for
Guidelines offer it broadly, with no minimum number of partners and nothing to justify.
It is particularly indicated in the following situations:
Asking for it is in itself a good enough reason to discuss it: if you think you are exposed, the consultation is the right place to say so. The doctor assesses the situation with you and suggests the schedule that fits.
The two schedules
Daily, or on demand around sex — equally effective when they are followed. Which ones are recommended, and how long they take to protect, depends on where you are.
In United Kingdom, daily PrEP is protective after 2 pills. For anal sex the tail is 2 pills after the last exposure; for receptive vaginal sex, protection is reached after 2 pills and the tail is 7 pills.
- Day 1One tablet a day, at the same time each day, with a meal.
- After 2 pillsProtection is established and lasts as long as you keep taking the tablet.
- StoppingKeep going for 2 more days after the last anal sex, or 7 days after receptive vaginal sex.
One tablet a day, at a fixed time, with food. This is the schedule recommended for receptive vaginal sex, chronic hepatitis B, and feminising hormone therapy.
- 2 to 24 h before2 tablets together.
- SexProtection is established about two hours after the double dose.
- 24 h later1 tablet.
- 48 h later1 tablet — then stop, if there has been no further sex.
Validated for anal sex, outside chronic hepatitis B and feminising hormone therapy. If sex continues: one tablet a day, stopping two days after the last exposure.
In United States, daily PrEP is protective after 7 pills. For anal sex the tail is 2 pills after the last exposure; for receptive vaginal sex, protection is reached after 21 pills and the tail is 28 pills.
- Day 1One tablet a day, at the same time each day, with a meal.
- After 7 pillsProtection is established and lasts as long as you keep taking the tablet.
- StoppingKeep going for 2 more days after the last anal sex, or 28 days after receptive vaginal sex.
One tablet a day, at a fixed time, with food. This is the schedule recommended for receptive vaginal sex, chronic hepatitis B, and feminising hormone therapy.
- 2 to 24 h before2 tablets together.
- SexProtection is established about two hours after the double dose.
- 24 h later1 tablet.
- 48 h later1 tablet — then stop, if there has been no further sex.
Not licensed by the regulator here, but the national guideline says it may be considered for men who have sex with men. Worth raising in consultation — it is not the default option in this country.
In Ireland, daily PrEP is protective after 7 pills. For anal sex the tail is 2 pills after the last exposure; for receptive vaginal sex, protection is reached after 7 pills and the tail is 7 pills.
- Day 1One tablet a day, at the same time each day, with a meal.
- After 7 pillsProtection is established and lasts as long as you keep taking the tablet.
- StoppingKeep going for 2 more days after the last anal sex, or 7 days after receptive vaginal sex.
One tablet a day, at a fixed time, with food. This is the schedule recommended for receptive vaginal sex, chronic hepatitis B, and feminising hormone therapy.
- 2 to 24 h before2 tablets together.
- SexProtection is established about two hours after the double dose.
- 24 h later1 tablet.
- 48 h later1 tablet — then stop, if there has been no further sex.
Validated for anal sex, outside chronic hepatitis B and feminising hormone therapy. If sex continues: one tablet a day, stopping two days after the last exposure.
In Canada, daily PrEP is protective after 7 pills. For anal sex the tail is 2 pills after the last exposure; for receptive vaginal sex, protection is reached after 21 pills and the tail is 28 pills.
- Day 1One tablet a day, at the same time each day, with a meal.
- After 7 pillsProtection is established and lasts as long as you keep taking the tablet.
- StoppingKeep going for 2 more days after the last anal sex, or 28 days after receptive vaginal sex.
One tablet a day, at a fixed time, with food. This is the schedule recommended for receptive vaginal sex, chronic hepatitis B, and feminising hormone therapy.
- 2 to 24 h before2 tablets together.
- SexProtection is established about two hours after the double dose.
- 24 h later1 tablet.
- 48 h later1 tablet — then stop, if there has been no further sex.
Validated for anal sex, outside chronic hepatitis B and feminising hormone therapy. If sex continues: one tablet a day, stopping two days after the last exposure.
In Somewhere else, daily PrEP is protective after 7 pills. For anal sex the tail is 2 pills after the last exposure; for receptive vaginal sex, protection is reached after 21 pills and the tail is 28 pills.
- Day 1One tablet a day, at the same time each day, with a meal.
- After 7 pillsProtection is established and lasts as long as you keep taking the tablet.
- StoppingKeep going for 2 more days after the last anal sex, or 28 days after receptive vaginal sex.
One tablet a day, at a fixed time, with food. This is the schedule recommended for receptive vaginal sex, chronic hepatitis B, and feminising hormone therapy.
- 2 to 24 h before2 tablets together.
- SexProtection is established about two hours after the double dose.
- 24 h later1 tablet.
- 48 h later1 tablet — then stop, if there has been no further sex.
Validated for anal sex, outside chronic hepatitis B and feminising hormone therapy. If sex continues: one tablet a day, stopping two days after the last exposure.
What we know about how well it works
Effectiveness does not depend on luck. It depends on regularity.
Studies that measured drug levels in the blood show it plainly: when the level matches a correctly taken regimen, infections are exceptional. That is also what explains the gap between the headline trial figures and the effectiveness seen in people who take their treatment as prescribed.
Side effects and precautions
The most common effects are digestive and short-lived; the points to watch are the kidneys and hepatitis B.
Before you start: the work-up
One consultation and one blood test are enough.
- 1HIV testEssential, with an assessment of any very recent exposure.
- 2HepatitisHepatitis B and C serologies, and a check of vaccination status (hepatitis A and B, HPV).
- 3STI screeningAccording to your practices: syphilis, chlamydia and gonorrhoea (throat, anus, urine, vagina).
- 4Kidney functionA creatinine test to check the kidneys before starting.
- 5The prescriptionDiscussion of the schedule, of contraception if relevant, and the prescription itself.
Follow-up, once you have started
An appointment roughly every three months: HIV test, STI screening, repeat prescription.
The rhythm can stretch from two to six months depending on your needs and your schedule. This follow-up is not administrative box-ticking: repeated STI screening is one of the best-documented indirect benefits of PrEP, because it catches infections that often have no symptoms.
Getting it, and what it costs
Who can prescribe PrEP and who pays for it differs by country — this is the part worth checking locally.
In United Kingdom, PrEP is free through public sexual health services, which also carry out the follow-up tests.
In United States, PrEP is covered through health insurance, and plans that follow the preventive-services rules must charge nothing for it, including the follow-up tests. Manufacturer and state assistance programmes exist if you are uninsured.
In Ireland, PrEP is free through public sexual health services, which also carry out the follow-up tests.
PrEP is available in Canada, but we could not confirm exactly how it is paid for. A sexual health clinic will know, and will also be able to tell you who can prescribe it locally.
PrEP is available in Somewhere else, but we could not confirm exactly how it is paid for. A sexual health clinic will know, and will also be able to tell you who can prescribe it locally.
Common questions
The questions that come up most often in consultation.
I missed a tablet, what should I do?
On the daily schedule, take it as soon as you remember, without doubling the next dose. One missed tablet does not cancel your protection, but repeated misses weaken it — more so for vaginal exposure. If you are unsure after sex, post-exposure treatment (PEP) is still possible within 48 hours at an emergency department or a sexual health clinic.
Can I stop whenever I want?
Yes, but not on the same day as your last sex. On the daily schedule you keep going for a few days afterwards, and on the on-demand schedule for two days. The exact tail depends on your country's guideline and on the kind of sex — the dosing section above gives your numbers. Tell your doctor if you have chronic hepatitis B, where stopping has to be supervised.
Do I still need condoms?
PrEP does not protect against other STIs. Condoms remain the only way to reduce that risk too, and the three-monthly screening built into the follow-up completes the picture.
I take hormones — is that compatible?
Yes. With feminising hormone therapy the daily schedule is recommended, as data on on-demand dosing are insufficient in that situation. There is no interaction with hormonal contraception either.
Will anyone be able to tell?
The tablet is a common generic with no mention of HIV on the box. In countries with anonymous testing centres, the whole process can stay off your medical record.