Learn About HIV Exposure Response Options

Understanding HIV Post-Exposure Prophylaxis (PEP)

Post-exposure prophylaxis, or PEP, is a preventive treatment option for people who believe they may have been exposed to HIV. PEP involves taking antiretroviral medications for 28 days following a potential exposure to the virus. The medications work by stopping HIV from establishing itself in your body after exposure, rather than treating an existing infection.

PEP is most effective when started as soon as possible after exposure—ideally within 2 hours, though research indicates it can still be beneficial up to 72 hours after exposure. The treatment consists of a combination of antiretroviral drugs, typically a three-drug regimen that prevents HIV from replicating in your system. Common medication combinations include tenofovir with emtricitabine plus raltegravir, or similar drug combinations that your healthcare provider may recommend based on your specific situation.

The effectiveness of PEP depends on several factors. When started within 2 hours of exposure, PEP is estimated to reduce the risk of HIV infection by more than 81%. When started between 2 and 72 hours after exposure, effectiveness decreases somewhat, but it still offers meaningful protection. Starting treatment after 72 hours is generally not recommended because the virus may have already begun to establish infection.

PEP is not a substitute for regular prevention methods like condoms or regular HIV testing. It is considered an emergency response to a specific exposure incident. This means it is not intended for people who have ongoing risks of exposure, as taking antiretroviral medications long-term as prevention is a different strategy called pre-exposure prophylaxis (PrEP).

Practical takeaway: If you believe you have had a potential HIV exposure, seek medical care immediately. Don't wait to see if symptoms develop—go to an emergency room, urgent care clinic, or HIV specialist as soon as possible, ideally within the first 2 hours. Write down the time of exposure and details about how it occurred so you can share this information with healthcare providers.

Types of Exposure That May Warrant PEP Consideration

Understanding what counts as a potential HIV exposure is important for deciding whether PEP may be relevant to your situation. HIV is transmitted through specific routes: blood, semen, vaginal fluids, rectal fluids, and breast milk. The virus does not spread through saliva, sweat, tears, urine, or feces. It also does not spread through air or by touching skin-to-skin contact with someone who has HIV.

Occupational exposures are one category where PEP may be considered. Healthcare workers, including nurses, doctors, laboratory technicians, and emergency responders, may be exposed to HIV-positive blood through needlestick injuries, cuts, or splashes to mucous membranes. A needlestick injury from a hollow-bore needle used for drawing blood carries a risk of approximately 0.3% if the source person has HIV. For cuts or splashes involving mucous membranes, the risk is lower. Healthcare facilities typically have protocols for evaluating these incidents and determining whether PEP is warranted.

Sexual exposures are another significant category. Unprotected vaginal or anal intercourse with a partner of unknown or positive HIV status may warrant PEP consideration. The risk varies depending on the type of sexual contact—anal receptive intercourse carries higher transmission risk (approximately 1.38% per act) compared to vaginal receptive intercourse (approximately 0.08% per act). If a condom breaks or slips during intercourse, this is considered a potential exposure. Oral sex carries lower but still measurable risk, particularly if there are cuts, sores, or other breaks in the mouth or genital area.

Other potential exposure scenarios include sharing injection equipment when using drugs, injuries from needles or sharp objects potentially contaminated with HIV-positive blood, and sexual assault. Sexual assault survivors may want to discuss PEP with a healthcare provider as part of their overall medical response and care plan.

Practical takeaway: Not every exposure to someone with HIV requires PEP. If the person with HIV has an undetectable viral load through consistent antiretroviral treatment (meaning the viral load is below 200 copies per milliliter), they cannot transmit HIV through sexual contact—a concept known as "undetectable equals untransmittable" or U=U. If you know the other person's HIV status and treatment status, share this information with your healthcare provider when discussing whether PEP is necessary.

How to Access PEP and What to Expect

Accessing PEP begins with contacting a healthcare provider as soon as you believe an exposure has occurred. Emergency rooms are available 24 hours a day and are equipped to evaluate potential HIV exposures and begin PEP treatment. Urgent care centers may also be able to help, though not all have HIV medications immediately available. Many hospitals have HIV specialists or infectious disease departments that handle these situations regularly.

When you contact a healthcare provider about a potential exposure, have information ready about when the exposure occurred, how it happened, and anything you know about the other person's HIV status or testing history. The healthcare provider will take a medical history, ask detailed questions about the exposure, and may perform an initial HIV test to establish your baseline status—confirming that you don't already have HIV before starting PEP.

After evaluating the situation, the healthcare provider will determine whether PEP is appropriate for your circumstances. They will discuss the potential benefits and side effects of the medications, answer your questions, and either start you on medications immediately or provide a referral to an HIV specialist or infectious disease clinic where you can begin treatment. The goal is to start PEP within 2 hours of exposure, so healthcare providers are trained to move quickly in these situations.

You will receive a month's supply of antiretroviral medications along with instructions on how to take them. These medications are taken by mouth, usually as pills, and may need to be taken at specific times each day. You will need to return for follow-up visits to assess how you are tolerating the medications, address any side effects, and obtain additional medication supplies. Follow-up visits typically occur at 1-2 weeks after starting PEP, and then again at the end of the 28-day course.

The total out-of-pocket cost for PEP varies depending on your insurance coverage and the specific medications prescribed. Many states and clinics offer PEP at reduced cost or no cost to uninsured individuals, though you may need to contact local health departments or HIV service organizations to learn about these programs in your area.

Practical takeaway: Keep a list of emergency rooms and urgent care centers near your home and workplace. If an exposure occurs after hours, you can go directly to the emergency room without calling ahead. Many emergency rooms now have protocols specifically for PEP evaluation, which speeds up the process.

Side Effects, Drug Interactions, and Health Considerations

Like all medications, the antiretroviral drugs used for PEP can cause side effects. Common side effects include nausea, vomiting, diarrhea, fatigue, headaches, and abdominal discomfort. These side effects are often mild to moderate and tend to improve over the first one to two weeks of treatment. Taking the medications with food, particularly high-fat foods, may help reduce nausea for some people. If side effects are severe or intolerable, your healthcare provider may be able to switch you to different medications that you tolerate better.

Kidney and liver function may be affected by some antiretroviral medications used in PEP regimens. For this reason, healthcare providers typically order baseline kidney and liver function tests before starting PEP and may repeat these tests during the 28-day course. People with existing kidney or liver disease should inform their healthcare provider, as this may affect which medications are recommended.

Antiretroviral medications can interact with other drugs you may be taking. Tell your healthcare provider about all medications you use, including over-the-counter medications, herbal supplements, and recreational drugs. Some combinations can reduce the effectiveness of PEP or increase side effects. Common interactions occur with certain antacids, some antibiotics, medications for seizures, and some heart medications. Your healthcare provider or pharmacist can review your complete medication list and address potential interactions.

If you are pregnant or could be pregnant, it is especially important to discuss this with your healthcare provider. Some antiretroviral medications used in PEP have been studied extensively in pregnancy and are considered relatively safe, while others have less safety