Key takeaways
- PEP must be started within 72 hours of a possible HIV exposure, and the sooner the better.
- You can walk in for PEP at our clinic near BTS Asok, every day from 09:00 to 21:00. No ID is needed, just a first name.
- PEP is a 28-day course. Take it at the same time each day and finish it, even if you feel well.
- Follow-up HIV tests at about 4–6 weeks and 3 months confirm that PEP has worked.
- If you are likely to be exposed again, ask about PrEP once you have finished PEP.
These are short answers to the questions we hear most often. Each one links to a fuller guide where it helps. If your question isn’t here, or you are worried about a recent exposure, contact us directly: a doctor can answer your specific situation in a way a web page cannot. For independent background reading, the UK charity i-base publishes a clear, plain-language guide to PEP and when it is used.
PEP at a glance
| Question | Quick answer |
|---|---|
| How soon must I start? | As soon as possible, ideally within 24 hours, and no later than 72 hours |
| How long is the course? | 28 days, usually one or two tablets a day |
| Do I need an appointment? | No, walk-ins are welcome every day, 09:00–21:00 |
| How long does the first visit take? | Usually about an hour, including your first dose |
| When are follow-up tests? | About 4–6 weeks and 3 months after the exposure |
| What do I need to bring? | Your first name, a list of any medicines you take, and the time of the exposure |
About PEP
How effective is PEP?
PEP greatly reduces the chance of HIV infection when it is started early and taken every day for 28 days. It is not 100% effective, and most failures are linked to a late start, missed doses or further exposures during the course.
Is it still worth starting PEP on day 3?
Yes, if you are still within 72 hours. PEP works best the earlier it starts, but a doctor will still offer it up to the 72-hour limit, so don’t let the time that has passed put you off.
Is PEP safe?
Modern PEP medicines are generally well tolerated. Some people have mild side effects such as nausea, tiredness or headache in the first week or two, and serious side effects are uncommon.
Does PEP protect against other STIs?
No, PEP only works against HIV and doesn’t prevent syphilis, gonorrhoea, chlamydia or hepatitis, so an STI check after an exposure is a good idea. Condoms remain the best everyday protection against most STIs.
Getting PEP in Bangkok
Do I need an appointment for PEP?
No. Walk-ins are welcome every day from 09:00 to 21:00. If you would like to let us know you are coming, you can message us by LINE or WhatsApp first.
What if I need PEP outside your opening hours?
Go to a hospital emergency department, which can often start PEP at any hour. You can then come to us during opening hours for follow-up and testing.
Can I just buy PEP at a pharmacy?
PEP should be started after a doctor’s assessment and a baseline HIV test. This makes sure it is needed, that you are HIV-negative before starting, and that the medicines are safe with anything else you take.
How do I know if my exposure needs PEP?
It depends on the type of exposure, the timing and what you know about the other person. Our guide to HIV risk and whether you need PEP includes a quick self-check, and a doctor can confirm.
What if my baseline HIV test is positive?
You would not start PEP. The doctor would explain your result calmly, arrange a confirmatory test, and talk you through treatment, which today allows people with HIV to live long, healthy lives.
What if I was sexually assaulted?
Your safety comes first. Call 1669 for emergency medical help or the Tourist Police on 1155. PEP, emergency contraception and STI care can all be started, and our step-by-step guide to what to do after a possible HIV exposure covers this with care.
While you take PEP
What time of day should I take PEP?
Any time that suits you, as long as it is roughly the same time every day. Many people link it to a daily habit, such as breakfast, and set a phone alarm. A weekly pill organiser also makes it easy to see at a glance whether today’s dose has been taken.
Can I take PEP with my other medicines or supplements?
Often, yes, but tell the doctor about everything you take. Some antacids and supplements containing calcium, iron or magnesium can affect certain PEP medicines unless doses are spaced apart.
What if I vomit soon after a dose?
Contact your clinic for advice on whether to repeat the dose. If nausea keeps happening, the doctor can suggest ways to manage it; our guide to PEP side effects and how to manage them has more tips.
Can I stop PEP early if my partner tests negative?
Only on a doctor’s advice. Sometimes new information, such as a partner’s recent test or undetectable viral load, means PEP can be stopped, but the doctor needs to weigh it up first.
Can I work, travel and exercise as normal?
Yes, most people carry on with daily life during PEP. Keep a spare dose in your bag in case you are out longer than planned. If you are flying across time zones, ask the doctor how to adjust your dosing time gradually.
After PEP
When will I know that PEP worked?
Follow-up HIV tests at around 4–6 weeks and 3 months after the exposure confirm your result. Our guide on when to test for HIV after an exposure explains the timings.
Are there symptoms that show PEP has failed?
Early HIV can cause flu-like symptoms, but so can many other things, including PEP side effects. Symptoms can’t tell you your status, so rely on your follow-up tests and contact a clinic if you feel unwell.
Can I take PEP more than once?
Yes. There is no set limit on how many times you can take PEP, and each exposure is assessed on its own. If you find you need PEP repeatedly, PrEP is usually a better way to protect yourself.
PrEP and testing
Can I start PrEP straight after finishing PEP?
Often, yes. Once a test confirms you are HIV-negative, many doctors recommend moving directly onto PrEP. Read PEP vs PrEP: the differences and who suits which.
How quickly can an HIV test detect a new infection?
No test can detect HIV immediately. A 4th-generation test picks up infection earlier than older antibody tests, but you still need to wait for the window period to pass for a reliable result.
Should I also be tested for other STIs?
Yes, especially after condomless sex or if you have symptoms. We screen for syphilis, hepatitis B and C, gonorrhoea and chlamydia, with same-day treatment where possible.
Privacy, cost and visitors
Do I need to show ID or a passport?
No. A first name is enough, and anonymous HIV testing is available. Consultations take place in private rooms.
How much does PEP cost?
The cost depends on the medicines and tests you need, so please message us for current prices before you visit. The doctor will also explain which tests are recommended for your situation and why.
I’m a tourist leaving Bangkok in a few days. Can I still take PEP?
Yes. You can take the full 28-day supply home, with a medical letter for your own doctor so follow-up tests can happen where you live. Our sexual health guide for travellers in Bangkok has more advice.
If your question is about a recent exposure, don’t wait for the perfect answer online. You can see what each visit includes on our PEP, PrEP and HIV testing services page, or message us by LINE or WhatsApp and a member of our team will help you take the next step.