What is HIV PEP?

HIV Post-Exposure Prophylaxis, commonly known as PEP, is an emergency medical intervention designed to prevent HIV infection after a potential exposure. It involves taking a combination of antiretroviral (ARV) medications daily for 28 days. These drugs work by stopping HIV from multiplying and establishing itself in the body’s immune system.

PEP is not a substitute for regular prevention methods like condoms or HIV PrEP (Pre-Exposure Prophylaxis). Instead, it’s a last-minute defence  like a fire extinguisher for moments when other safety measures fail. That includes situations like:

• A broken or slipped condom during sex
• Sex with a partner of unknown HIV status
• Shared needles during drug use
• Accidental needle-stick injuries in healthcare settings
• Sexual assault or coerced sex

PEP must be started within 72 hours of the potential exposure. The earlier it’s taken, the more effective it is. Ideally, treatment should begin within 2 hours. Every hour counts.

The World Health Organization (WHO), U.S. Centers for Disease Control and Prevention (CDC), and Singapore’s Action for Aids all have information on the use of HIV PEP as a key tool in reducing new HIV infections particularly in settings where HIV remains prevalent or where healthcare access is uneven.

It’s important to note that PEP is not always necessary for every exposure. A doctor will help assess your risk based on the type of contact, timing, and whether the source is known to be HIV-positive.

Who Should Consider PEP?

Anyone who thinks they may have been exposed to HIV, even if unsure, should speak to a doctor immediately. Because PEP is most effective within 72 hours, decisions need to be made quickly.

1. Sexual Exposure

If you’ve had vaginal or anal sex without a condom (or the condom broke or slipped), and you don’t know the HIV status of your partner, or you know they are HIV-positive and not virally suppressed, you may be at risk.

This includes one-time hookups, casual relationships, or long-term partners if one’s HIV status or treatment adherence is uncertain.

Also consider PEP if you’ve had:

• Group sex or anonymous sex
• Sex under the influence of drugs or alcohol and can’t recall details
• Exposure to blood during sex (e.g., rough play, menstruation)

2. People Facing Higher Exposure Risk

Some people may face frequent or unpredictable exposure risks due to lifestyle, work, or social context. This includes:

• Sex workers who may not always be able to negotiate condom use
• People with multiple or anonymous partners (regardless of gender)
• Men who have sex with men (MSM), due to statistical prevalence
• Transgender individuals, especially in settings where healthcare is less accessible
• People who inject drugs, particularly when sharing needles

These groups are not inherently “high risk” but may face higher exposure, compounded by stigma, discrimination, and inconsistent access to healthcare and information.

3. Healthcare Workers

If you’re a nurse, doctor, lab technician, or cleaner who had a needle-stick injury or came into contact with infected bodily fluids through broken skin or mucous membranes, PEP may be appropriate. Time is critical here, even more so than in sexual exposure, as incidents are usually reported immediately.

Institutions are required to provide rapid access to PEP and monitor follow-up testing, including assessments at 6 weeks, 3 months, and 6 months.

4. Survivors of Sexual Assault

HIV PEP is part of the standard post-assault care package in most hospitals and trauma units. Even if the risk of HIV is low, doctors may recommend it as a precaution, especially if the assailant’s status is unknown or known to be positive.

In these cases, PEP is usually provided alongside emergency contraception, STI screening, hepatitis B vaccination (if required), and referrals for mental health support.

Important: You don’t need to wait for test results from the other party to begin PEP. In almost all guidelines, including Singapore’s, treatment should not be delayed while waiting for confirmation.

How Effective is HIV PEP?

When taken correctly and started promptly, HIV PEP can reduce the risk of HIV infection by over 80%. That number might seem low at first glance, but remember: this figure includes people who started late, missed doses, or discontinued treatment early.

Studies show that when PEP is taken consistently, on time, and for the full 28 days, the real-world effectiveness approaches closer to 90–95%, especially in lower-exposure cases.

What Factors Affect PEP’s Effectiveness?

• Time to initiation: Starting within 2 hours is ideal; after 72 hours, it’s often too late.
• Adherence: Missing doses or stopping early significantly reduces effectiveness.
• Exposure type: Anal sex carries more risk than vaginal; blood exposure is higher risk than saliva.
• Viral load of the source: Higher viral loads increase the risk of transmission.

PEP is not a guarantee. But it dramatically reduces the chance of infection, especially when combined with follow-up testing, STI screening, and (if applicable) a switch to PrEP for future prevention.

When and How Fast to Start

Time is everything. If you wait too long, even the best medications won’t be able to stop the virus from spreading in your body. HIV can begin replicating within hours of entering your bloodstream. Once replication begins, the effectiveness of PEP drops rapidly.

• Best timing: Within 2 hours of exposure
• Acceptable window: Up to 72 hours (3 days)
• Not recommended: After 72 hours — although follow-up testing is still important

What to Do Immediately:

1. Wash any exposed area with soap and water (do not scrub harshly).
2. Avoid self-medicating, don’t take leftover HIV meds.
3. Head to a clinic that provides PEP. Call ahead if you’re unsure.
4. Be prepared to describe what happened and when.
5. Ask about other STI and hepatitis screenings.

Where Can You Get HIV PEP in Singapore?

HIV PEP is available at both private and public healthcare facilities across Singapore. Access is fast, discreet, and supportive in most settings. If you need PEP, head to any of the following:

• Shim Clinic: Offers walk-in consultations and same-day prescriptions. No referral is needed.
• Public hospitals: Emergency departments are open 24 hours and provide PEP assessments around the clock.
• DSC Clinic and polyclinics: Some government clinics offer PEP during operating hours.
• Community NGOs: Action for AIDS and similar organisations can help guide you or refer you for treatment.

Wherever you go, bring any information you can about the exposure event. That includes timing, what happened, and whether the source is known. The more your doctor knows, the better they can help you decide if PEP is appropriate.

You’ll likely undergo a rapid HIV test, a consultation, and be prescribed a full 28-day course of medication. Some places may provide an initial 3-day supply with follow-up to complete the rest.

What to Expect When You Start HIV PEP

Visiting a clinic for PEP doesn’t have to be intimidating. Most providers understand that time is of the essence and will guide you through the process as efficiently as possible. Here’s what typically happens during your visit:

• Risk assessment: The doctor will ask when and how the exposure happened, who it involved, and if the source is known or unknown.
• Baseline HIV test: A rapid test is done to confirm that you are currently HIV-negative before starting the medication.
• Medication prescription: You will receive a full 28-day supply or an initial starter pack with instructions for follow-up.
• Counselling and education: The doctor or nurse will explain how to take the medication, what side effects to expect, and when to return for testing.

At Shim Clinic, walk-in consultations are private and judgment-free. Public hospitals also offer PEP, though they may require longer wait times. Cost varies depending on where you go and what is prescribed, but most private clinics charge between SGD 400 to 700 for the full course.

What Medications Are Used for HIV PEP?

The standard HIV PEP regimen includes two types of drugs: nucleoside reverse transcriptase inhibitors (NRTIs) and an integrase strand transfer inhibitor (INSTI). The most commonly prescribed medications in Singapore include:

• Tenofovir disoproxil fumarate (TDF) + Emtricitabine (FTC): These are taken together as a single pill once daily.
• Raltegravir (RAL) or Dolutegravir (DTG): One of these is taken separately, either once or twice daily, depending on the drug.

This combination is effective and widely used because it works quickly, is generally well tolerated, and has a low risk of drug resistance. Your doctor will choose the right combination based on your medical history and any potential drug interactions.

Common Side Effects and How to Manage Them

Most people taking PEP experience only mild side effects. These usually occur in the first few days and then improve. Common side effects include:

• Nausea or upset stomach
• Headaches
• Fatigue or tiredness
• Insomnia or vivid dreams

You can take the medication with food to reduce stomach discomfort. Staying hydrated, getting enough sleep, and avoiding alcohol during the first few days can also help reduce symptoms.

Can HIV PEP cause flu-like symptoms?

Yes. Some people report symptoms like fever, body aches, or chills shortly after starting PEP. These are side effects of the medication, not signs of HIV infection. If symptoms persist or worsen, it’s a good idea to check in with your doctor.

Will I need monitoring or blood tests?

Yes. Your doctor may request blood tests during or after the course of treatment to monitor kidney and liver function, especially if you’re taking other medications or have underlying health issues. This ensures the treatment is safe for your body.

Real-World Questions People Are Asking

Can I drink alcohol while taking HIV PEP?

Yes, but in moderation. Alcohol does not interact directly with PEP medications. However, drinking too much may increase your chances of forgetting a dose or engaging in higher-risk behavior. If you drink, stay mindful and stick to your schedule.

What happens if I miss a dose?

Take the missed dose as soon as you remember. If it’s close to your next scheduled time, skip the missed one and continue as normal. Do not double up. Missing one dose is not the end of the world, but repeated missed doses can reduce the protection PEP provides.

Can I stop taking HIV PEP if I feel fine?

No. You must complete the full 28-day course to ensure the highest level of protection. Stopping early can allow the virus to replicate and reduce the effectiveness of the treatment.

Can I be infected while on HIV PEP?

It is possible, especially if you started late, missed doses, or had a high-risk exposure. While PEP greatly reduces the risk of infection, it is not 100 percent guaranteed. That’s why follow-up testing is important.

How long does HIV PEP stay in your system?

The medications are cleared from your body within a few days after completing the course. However, some people may feel lingering fatigue or mild gastrointestinal symptoms for a week or two afterward. These effects are temporary and not harmful.

Does HIV PEP weaken the immune system?

No. PEP medications do not suppress your immune system. In fact, they help protect it by preventing HIV from establishing infection. Some side effects might feel like being unwell, but they do not reflect a weakened immune response.

What Happens After You Finish the 28-Day Course?

Completing the full course of PEP is an important milestone, but the process doesn’t end there. Follow-up is essential to confirm your HIV status and protect your long-term health. Here’s what typically comes next:

• HIV testing at 4 to 6 weeks: This checks for any early signs of infection.
• Final HIV test at 3 months: This confirms whether or not HIV transmission occurred.
• STI screening: Your doctor may also recommend tests for other infections like syphilis, gonorrhea, or hepatitis.
• PrEP discussion: If you may face future exposures, your doctor may suggest switching to PrEP for ongoing protection.

Most people complete PEP without complications and go on to stay HIV-negative. Clinics like Shim Clinic will guide you through this follow-up process and offer counselling or support if you need it.

Is It Safe to Take PEP More Than Once?

Yes, PEP can be taken more than once if needed. Life is unpredictable and sometimes exposures happen again. However, repeated courses of PEP may indicate that you could benefit from a more proactive strategy like PrEP.

PrEP is a daily pill or long-acting injection that offers continuous HIV prevention. It is ideal for people who may be exposed regularly or want added peace of mind. Talk to your doctor about whether PrEP fits your needs and lifestyle.

Also note that taking PEP frequently means your doctor will want to monitor your kidney and liver health over time. Always inform them about your history with PEP so they can offer the best advice for future prevention plans.

Take Action When It Matters Most

HIV PEP is not something to be ashamed of. It is a powerful, medically endorsed option for people who care about their health and want to take control after a stressful or risky event.

If you’ve had a potential exposure to HIV, don’t wait. Every hour counts. The sooner you start, the more protected you are.

Shim Clinic is here to support you with fast access to HIV PEP, compassionate healthcare, and professional advice.

Walk in. Ask questions. Get protected.