PrEP (pre-exposure prophylaxis) is taken as one pill daily, as an on-demand schedule before and after sex, or as an injection every two months. The method you use determines the exact timing, but all three options require an HIV test and kidney function check before you start. Here’s how each approach works in practice.
Daily Oral PrEP
The most common way to take PrEP is one pill, once a day, at roughly the same time each day. You take it every day regardless of whether you have sex, use drugs, or do anything that could expose you to HIV. Two oral PrEP medications are approved for daily use: Truvada and Descovy. Your provider will help determine which one is right for you based on your kidney health and the type of exposure you’re protecting against.
There’s no strict rule about taking it with food, but some people find that taking it with a meal or snack reduces stomach discomfort, especially in the first few weeks. Pick a time that fits your routine, whether that’s morning, evening, or alongside another daily habit like brushing your teeth. Consistency matters more than the specific hour.
How Long Until You’re Protected
Daily PrEP does not provide full protection immediately. The medication needs time to build up to protective levels in the tissues where HIV could enter your body. For receptive anal sex, this generally takes about 7 days of consistent daily use. For vaginal sex or injection drug use, the timeline is longer, typically around 21 days. During that ramp-up period, use other prevention methods like condoms.
The On-Demand (2-1-1) Method
If you don’t have frequent exposure and prefer not to take a daily pill, the 2-1-1 schedule is an option that has been studied for men who have sex with men. It works like this:
- 2 pills, 2 to 24 hours before sex. This is your loading dose. The earlier end of that window (closer to 24 hours before) gives the drug more time to reach protective levels.
- 1 pill, 24 hours after the first dose.
- 1 pill, 24 hours after the second dose.
The timing here is critical. Taking those two initial pills less than 2 hours before sex does not provide adequate protection. And you cannot skip the follow-up doses; the two pills taken afterward help clear any virus that may have entered your body. This method uses Truvada only and has not been studied for vaginal sex or injection drug use.
Injectable PrEP
If you’d rather skip pills entirely, injectable PrEP (cabotegravir, sold as Apretude) is given as a shot in the buttock muscle at a clinic. The schedule has two phases:
- Initiation: Two injections given one month apart.
- Maintenance: One injection every two months, continuing for as long as you want protection.
Some providers offer a short course of oral cabotegravir pills before the first injection so you can check for side effects. If you go that route, the first injection happens on the last day of the oral lead-in or within three days after. Others skip the oral phase and go straight to injections. Either way, keeping your injection appointments on schedule is essential since gaps in coverage can leave you vulnerable.
What to Do If You Miss a Dose
If you’re on daily oral PrEP and realize you missed a dose, take it as soon as you remember. The exception: if it’s within 8 hours of your next scheduled dose, skip the missed one and resume your normal schedule. Do not double up by taking two pills at once.
Missing a pill here and there is not ideal but probably won’t eliminate your protection entirely. However, if you miss four or more doses in any given week, your protection drops substantially. If that happens and you’ve had a potential HIV exposure during that time, contact your provider or a PrEP hotline promptly, because you may need post-exposure prophylaxis (PEP) instead.
Early Side Effects
Some people experience nausea, diarrhea, headache, fatigue, or stomach pain when they first start oral PrEP. These “start-up” symptoms are usually mild and tend to fade within the first few weeks as your body adjusts. If side effects persist beyond a month or become disruptive, that’s worth bringing up with your provider, since switching formulations sometimes helps.
Tests Before and During Treatment
Before you can start any form of PrEP, you’ll need a confirmed negative HIV test. Taking PrEP while unknowingly HIV-positive can lead to drug resistance, which limits future treatment options. You’ll also have blood drawn to check kidney function, since oral PrEP is processed through the kidneys. Truvada requires a kidney clearance rate above 60 mL/min, while Descovy can be used with clearance as low as 30 mL/min. If your kidney function is below 30, injectable PrEP is the recommended alternative.
Once you’re on PrEP, expect follow-up visits every three months. These typically include repeat HIV testing, kidney function monitoring for oral PrEP users, and screening for sexually transmitted infections. These appointments aren’t optional extras; they’re part of what makes PrEP safe to use long term. The small decreases in kidney function that oral PrEP can cause are generally minor and reverse after stopping the medication, but catching any problems early is the whole point of regular monitoring.
Drug Interactions to Watch For
Because oral PrEP is filtered through the kidneys, other medications that stress the kidneys can cause problems when combined. High-dose or frequent use of NSAIDs (like ibuprofen or naproxen) is one common concern. Antiviral drugs used for herpes or other infections, such as acyclovir and valacyclovir, are also processed by the kidneys and can interact. If you regularly take any of these, your provider may monitor your kidney function more closely or recommend injectable PrEP instead.
Storing Your Medication
Keep oral PrEP at room temperature, between 68°F and 77°F. Store it in its original container with the lid tightly closed. If there’s a small desiccant packet inside (the little silica gel packet), leave it in, as it protects the pills from moisture. Avoid transferring pills to a weekly organizer for long-term storage, since removing them from the sealed container exposes them to humidity that can degrade the medication over time. If you use a pill organizer for convenience, refill it weekly rather than monthly.