PrEP and PEP in Chiang Mai: what is the difference?
A clear explanation of PrEP and PEP for English-speaking patients in Chiang Mai — what each is for, how they are different, what tests are involved, and how Klaibaan Clinic can help.
Quick answer
PrEP and PEP are both HIV prevention medications, but they serve very different purposes. PrEP is taken before possible exposure — it is a planned, ongoing prevention approach. PEP is taken after a possible exposure — it is an emergency measure that must be started as soon as possible, generally within 72 hours. A doctor's assessment is required for both, and they are not interchangeable.
PrEP: prevention before exposure
PrEP stands for Pre-Exposure Prophylaxis. It is an antiretroviral medication taken by HIV-negative people before possible HIV exposure to significantly reduce the risk of acquiring HIV.
Key points about PrEP:
- It is planned and ongoing. PrEP is not a one-time dose — it requires regular, consistent use to be effective, along with regular medical follow-up.
- It is for HIV-negative people. A negative HIV test is required before starting PrEP. PrEP is not appropriate for people who already have HIV.
- Baseline testing is needed. Before starting PrEP, the doctor will typically arrange an HIV test, kidney function test, and hepatitis B review. Some STI testing may also be appropriate.
- Follow-up is required. PrEP requires regular check-ins — typically every 3 months — for HIV testing, kidney monitoring, and STI screening.
- It does not protect against other STIs. PrEP reduces HIV risk but does not prevent syphilis, gonorrhea, chlamydia, or other sexually transmitted infections. Regular STI testing remains important.
Who might consider PrEP? PrEP may be appropriate for HIV-negative individuals with ongoing HIV risk — for example, those in relationships where one partner has HIV, or those who feel that consistent HIV prevention is important for their situation. A doctor will assess suitability and discuss the commitment involved.
PEP: urgent assessment after possible exposure
PEP stands for Post-Exposure Prophylaxis. It is an antiretroviral medication course taken after a possible HIV exposure, to reduce the risk of HIV transmission.
Key points about PEP:
- It is time-sensitive. PEP must be started as soon as possible after a possible exposure — ideally within a few hours and generally within 72 hours. After 72 hours, PEP is typically no longer considered appropriate and will not be recommended.
- It is not a guarantee. When taken correctly and promptly after a genuine exposure, PEP can significantly reduce HIV risk. It is not 100% effective, and adherence to the full course is important.
- Doctor assessment is required. The doctor will assess the timing of the exposure, the type of exposure, the HIV status of the source if known, your current HIV status, and other medical factors before PEP can be discussed.
- Baseline tests are needed. A baseline HIV test is required before PEP can be started. Other tests (kidney function, hepatitis B) may also be appropriate.
- It is a 28-day course. PEP is typically a daily medication course for approximately 28 days. Completing the full course is important.
- Follow-up HIV testing is needed. After completing PEP, follow-up HIV testing is recommended at specific intervals — the doctor will advise on timing.
- It is not for repeated routine exposures. PEP is an emergency measure, not a substitute for ongoing prevention. If you find yourself needing PEP repeatedly, the doctor may discuss PrEP as a more appropriate long-term approach.
PrEP vs PEP: a simple comparison
PrEP
When: Before possible exposure (ongoing)
For: HIV-negative people with ongoing risk
Timing: Planned and routine
Duration: Ongoing with regular monitoring
Tests needed: HIV, kidney, hepatitis B, STI screening
PEP
When: After possible exposure (emergency)
For: Anyone with a recent possible HIV exposure
Timing: Urgent — ideally within hours, maximum 72 hours
Duration: Approximately 28 days
Tests needed: HIV, kidney, hepatitis B baseline
What tests are involved?
Both PrEP and PEP require medical assessment and baseline testing before they can be considered. Tests that may be discussed include:
- HIV test: required before starting either PrEP or PEP. For PrEP, confirms HIV-negative status. For PEP, confirms current status before starting treatment.
- Kidney function (creatinine, eGFR): some antiretroviral medications used for PrEP can affect kidney function. A baseline kidney test is standard before starting PrEP and may also be done for PEP.
- Hepatitis B testing: relevant because some antiretroviral medications affect hepatitis B, and hepatitis B co-infection changes the management approach.
- STI screening: recommended before starting PrEP and at regular follow-up visits. People on PrEP are typically screened for syphilis, gonorrhea, chlamydia, and other STIs every 3 months.
When hospital or emergency care is the safest option
Go directly to hospital or emergency department for:
- Sexual assault — for comprehensive care, forensic documentation, PEP assessment, and emergency support
- A possible PEP-eligible exposure outside clinic hours — hospital assessment is the fastest route
- Severe injury associated with the exposure
- Any situation where you feel unsafe or need emergency support
PEP assessment is time-sensitive. During clinic hours, contact Klaibaan Clinic promptly. Outside opening hours, go to the nearest hospital or emergency department and explain that you need PEP assessment after a recent possible HIV exposure.
How Klaibaan Clinic can help
Klaibaan Medical Clinic in San Sai, Chiang Mai provides PrEP and PEP consultation for English-speaking patients. The doctor can:
- Assess whether PrEP or PEP may be appropriate for your situation
- Arrange baseline HIV testing and other relevant tests
- Explain the medication, follow-up requirements, and what to expect
- Monitor kidney function and arrange regular HIV and STI testing for patients on PrEP
- Discuss PrEP as an ongoing prevention option if PEP is being considered for repeated situations
For PEP, contact the clinic as soon as possible after a possible exposure during opening hours. Outside opening hours, go directly to a hospital. Time matters for PEP.
Common questions
What is the difference between PrEP and PEP?
PrEP (pre-exposure prophylaxis) is medication taken before possible HIV exposure to reduce the risk of acquiring HIV. It is planned and ongoing. PEP (post-exposure prophylaxis) is medication taken after a possible HIV exposure, as an emergency measure. PEP is time-sensitive and should be started as soon as possible, ideally within hours and generally within 72 hours of a possible exposure. The two serve different purposes and are not interchangeable.
Do I need tests before starting PrEP or PEP?
Yes. Before starting PrEP, an HIV test is required to confirm you are HIV-negative, as PrEP is not appropriate for people who already have HIV. Kidney function and hepatitis B testing are also typically recommended. For PEP, an HIV test before starting is standard, along with other baseline assessments. The doctor will advise on what is needed based on your situation.
Does PrEP or PEP protect against STIs other than HIV?
No. PrEP and PEP are specific to HIV prevention. They do not protect against other sexually transmitted infections such as syphilis, gonorrhea, chlamydia, or herpes. Regular STI testing is recommended alongside PrEP for people with ongoing risk, as STIs can be present without symptoms.
Who might want to consider PrEP?
PrEP may be considered by HIV-negative individuals who have ongoing risk of HIV exposure and want to reduce that risk. This can include people in serodiscordant relationships (where one partner has HIV), people with multiple partners, or others who feel that ongoing HIV prevention is appropriate for their situation. A doctor will assess whether PrEP is suitable and discuss the commitment involved.
Can Klaibaan Clinic help with PrEP or PEP consultation?
Yes. Klaibaan Medical Clinic in San Sai, Chiang Mai provides PrEP and PEP consultation for English-speaking patients. This includes doctor assessment, baseline HIV and kidney function testing, and follow-up planning. For PEP, contact the clinic as promptly as possible. Outside clinic opening hours, hospital or emergency department assessment may be the fastest option for time-sensitive PEP care.
Sources and related reading
Selected official sources and clinic pages used to keep this guide practical and medically responsible.
Need confidential advice before visiting?
Message Klaibaan Medical Clinic on LINE or call during opening hours. The clinic provides English-friendly PrEP and PEP consultation in San Sai, Chiang Mai.