What PrEP is and what it is not
PrEP stands for pre-exposure prophylaxis. It refers to the preventive use of certain HIV medicines by HIV-negative people to prevent HIV infection. PrEP is not a substitute for medical care, but part of a structured prevention approach including testing, counselling and regular monitoring. WHO: Pre-exposure prophylaxis.
It is important to be clear: PrEP protects against HIV, but not against other sexually transmitted infections (STIs). Tests, condoms and, where appropriate, vaccinations remain relevant for those infections.
How well PrEP protects
When taken correctly, PrEP is highly effective. Large studies and public health data show that the risk of HIV from sexual contact can be reduced by about 99 per cent when PrEP is taken regularly. CDC: PrEP effectiveness.
The percentage alone is not the only point to consider; it is the underlying principle that matters. PrEP works reliably when sufficient drug levels are present in the body during the critical period. Irregular dosing is the most common reason for reduced protection.
Who PrEP may be suitable for
PrEP is aimed at situations with an increased risk of HIV, not at specific identities. It may be appropriate when other prevention strategies are insufficient or cannot be implemented reliably.
Typical scenarios include:
- sex with partners whose HIV status is unknown or for whom sustained viral suppression is not known
- frequently changing sexual partners, particularly without consistent condom use
- sex work, depending on the circumstances and available protection
- partnerships with an HIV-positive person without confirmed sustained viral suppression
- situations where injecting equipment may be shared
Whether PrEP fits into your life is best determined in a short, structured consultation.
PrEP dosing regimens
Daily oral PrEP is the international standard. Event-driven regimens also exist, but these have not been studied equally across all populations and are not recommended everywhere.
Daily PrEP
For daily PrEP one tablet is taken each day. The advantage is a steady drug level and a simple routine. For many people this is the most reliable option because it is independent of individual encounters.
Event-driven PrEP
Event-driven (on-demand) PrEP is taken around anticipated sexual encounters. It requires precise timing and is not suitable for everyone or every situation. Medical counselling is particularly important here.
How soon PrEP provides protection
How quickly PrEP protects depends on the dosing regimen, the tissue involved and the type of exposure. For this reason, guidelines deliberately tend to be conservative and emphasise individual counselling at the start.
In the initiation phase it is sensible to take PrEP consistently and avoid shortcuts, even if the perceived risk seems low.
Which tests and monitoring are required
PrEP always requires medical supervision. Before starting, an HIV infection must be reliably excluded, and regular monitoring is necessary during use. HIV testing is often recommended about every three months, supplemented by further investigations depending on the risk profile. Public health authority: FAQ on HIV PrEP.
Typically this includes:
- HIV testing before starting and at regular intervals
- testing for other sexually transmitted infections
- monitoring of kidney function
- counselling on dosing, side effects and interactions
This structure serves safety. It is particularly important to reliably exclude HIV before starting, because PrEP is not suitable for treating an existing infection.
Side effects and tolerability
Most people tolerate PrEP well. In the first days or weeks mild complaints such as nausea, headache or fatigue may occur and usually resolve. Long-term concerns mainly relate to kidney function and, in certain situations, bone density, which is why regular monitoring is included.
A current clinical guideline provides orientation on HIV pre-exposure prophylaxis. Clinical guideline: S2k guideline on HIV pre-exposure prophylaxis.
Interactions and concomitant medication
Drug interactions are overall uncommon but not impossible. Particular attention should be paid to medicines or conditions that can affect the kidneys. Open communication about all regularly taken medicines is part of safe use.
PrEP in relationships
In stable relationships, PrEP can provide temporary additional security, for example if a partner's HIV status is unclear or sustained viral suppression has not yet been demonstrated. A shared plan is more helpful than unspoken assumptions.
If an HIV-positive person has a persistently undetectable viral load, the sexual transmission risk is generally extremely low. Nevertheless, PrEP can be reassuring during transitional phases or when there is uncertainty.
PrEP, pregnancy and trying to conceive
PrEP can play a role around conception or pregnancy in certain situations, for example in serodiscordant partnerships. In such cases individual counselling is especially important to balance benefits and monitoring appropriately.
Making practical use of PrEP in everyday life
PrEP works best when it is part of a clear plan. This includes regular dosing, testing and a realistic approach to risk.
- treat PrEP as a fixed routine
- attend monitoring appointments reliably
- seek medical advice promptly if you have symptoms or concerns
- view STI testing as a normal part of sexual health
Costs and practical planning
Access and costs vary considerably between countries. In some places PrEP is part of public healthcare, elsewhere it is privately funded or tied to specific programmes.
If you travel or stay abroad for an extended period, you should clarify in advance how testing, prescriptions and supplies can be organised.
Legal and regulatory context
Prescription requirements, monitoring expectations, cost coverage and available preparations differ by country. These rules can change and should be checked for the current situation.
For international readers: PrEP should always be used in accordance with local medical and legal requirements.
Myths and facts about PrEP
- Myth: PrEP protects against all sexually transmitted infections. Fact: PrEP protects against HIV, not against other STIs.
- Myth: PrEP is only for certain groups. Fact: What matters are risk situations, not identities.
- Myth: People on PrEP do not need tests. Fact: Regular testing is a central part of safe use.
- Myth: PrEP necessarily damages the kidneys. Fact: Most people tolerate PrEP well; monitoring serves prevention.
- Myth: Irregular dosing is sufficient. Fact: Protection depends strongly on reliable dosing.
- Myth: PrEP and PEP are identical. Fact: PrEP is preventive; PEP is used after a possible exposure.
When medical advice is particularly important
Even while on PrEP there are situations where renewed medical advice is sensible or necessary.
- symptoms that could indicate acute HIV infection
- long interruptions in dosing
- new medications or conditions that may affect the kidneys
- pregnancy, breastfeeding or a concrete plan to conceive
- repeated STI diagnoses requiring an adjustment of prevention strategies
Conclusion
PrEP is a highly effective and well-researched method of HIV prevention when used correctly. It does not replace testing or medical supervision but can significantly contribute to safety as part of a clear prevention plan. Key factors are realistic expectations, reliable dosing and regular monitoring.
An impartial government overview with up-to-date basic information is available from HIV.gov. HIV.gov: Pre-exposure prophylaxis.
