PrEP: A Complete Guide to Pre-Exposure Prophylaxis for HIV Prevention

Introduction

PrEP (pre-exposure prophylaxis) is a breakthrough in HIV prevention, offering highly effective protection for people at risk of HIV infection. When taken correctly, PrEP reduces the risk of acquiring HIV from sex by about 99% and from injection drug use by at least 74%. With both daily pills and long-acting injections now available, PrEP is a safe and proven method for people who do not have HIV but want to protect themselves from exposure.

This guide explains what PrEP is, how it works, who should consider taking it, and what you need to know before starting PrEP.

What is PrEP?

PrEP stands for pre-exposure prophylaxis, a medical strategy that uses HIV medicines to prevent infection before potential exposure. The word “prophylaxis” means prevention.

The U.S. Food and Drug Administration (FDA) has approved four medicines for PrEP:

Truvada (or generic equivalent): a pill taken daily.
Descovy (or generic equivalent): a pill taken daily (not recommended for women at risk through vaginal sex).
Apretude: an injection taken every two months.
Yeztugo: an injection taken every six months.

Which option you use depends on your lifestyle, health needs, and risk level.

PrEP works by blocking HIV’s ability to establish infection in the body. When taken consistently as prescribed, PrEP maintains protective levels of medicine in the bloodstream, preventing the virus from spreading if exposure occurs.

Who Should Consider Taking PrEP?

PrEP is intended for people who are HIV-negative but at high risk of exposure. It is not designed for those who already have HIV.

The CDC recommends PrEP if you are HIV-negative and in the past six months you have:

Had anal or vaginal sex without a condom.
Had a sexual partner with HIV, particularly if their viral load is detectable or unknown.
Been diagnosed with a sexually transmitted infection (STI).

PrEP is also recommended for people who inject drugs and:

Share needles, syringes, or other injection equipment.
Have an injection partner who has HIV.

PrEP may also be considered if you:

Have used post-exposure prophylaxis (PEP) multiple times.
Report ongoing unsafe sex practices after using PEP.

If you believe PrEP may be right for you, consult a healthcare provider to discuss your options.

How Well Does PrEP Work?

PrEP is one of the most effective HIV prevention methods available today. Its effectiveness depends on adherence—taking the medication consistently as prescribed.

Oral PrEP (Truvada or Descovy): Daily use reduces the risk of getting HIV from sex by about 99%. For injection drug users, it reduces risk by at least 74%.
Injectable PrEP (Apretude or Yeztugo): Clinical studies show injections are just as effective as daily pills, with the added benefit of not requiring daily adherence.

It’s important to note:

Descovy is not recommended for women at risk of HIV from vaginal sex, as its effectiveness has not been studied in this group.
While PrEP prevents HIV, it does not protect against other STIs. Using condoms along with PrEP provides broader protection.

PrEP vs. PEP: What’s the Difference?

It’s easy to confuse PrEP and PEP, but they serve different purposes:

PrEP (Pre-Exposure Prophylaxis): Taken before exposure, either daily or through long-acting injections, to reduce the chance of HIV infection.
PEP (Post-Exposure Prophylaxis): Taken after a possible exposure, usually within 72 hours, and continued for 28 days.

PEP is for emergencies, while PrEP is designed for ongoing prevention in people who are frequently at risk.

How to Take PrEP

The way you take PrEP depends on whether you choose pills or injections.

Oral PrEP (Truvada or Descovy)

Daily dosing: Take one pill every day at the same time.
On-demand dosing: Some individuals take PrEP “on demand” using the “2-1-1” schedule:
- Take two pills 2–24 hours before sex.
- Take one pill 24 hours later.
- Take another pill 24 hours after that.
  This method is not FDA- or CDC-approved and should only be used under medical supervision.

Injectable PrEP (Apretude or Yeztugo)

Apretude: Injection every two months.
Yeztugo: Injection every six months.
In some cases, an initial oral dose may be required before your first injection.

Regardless of the form, missing doses reduces effectiveness. Stick to your schedule for maximum protection.

Does PrEP Cause Side Effects?

PrEP is generally safe, but like all medicines, it can cause side effects in some people.

Common Side Effects

Nausea
Diarrhea
Headaches
Insomnia
Fatigue

These usually disappear after the first few weeks.

Rare Side Effects

Kidney problems
Liver issues
Lactic acidosis (very rare)

Before starting PrEP, your healthcare provider will run tests to ensure the medication is safe for you. If you experience side effects that don’t go away, consult your provider immediately.

HIV Testing and Monitoring While on PrEP

To use PrEP safely, regular medical follow-up is required.

HIV test: You must test negative before starting PrEP.
Ongoing testing: HIV testing is required every three months for oral PrEP users and before each injection for injectable PrEP.
Kidney and liver function tests: Periodically monitored to ensure no complications.

If you test positive for HIV while on PrEP, your provider will switch you to an HIV treatment regimen rather than prevention medicines.

Benefits of PrEP

High effectiveness: Up to 99% protection from sexual transmission.
Flexible options: Daily pills or long-acting injections.
Peace of mind: Reduces anxiety about HIV exposure.
Combination protection: Works best when combined with condoms and STI testing.

Limitations of PrEP

While PrEP is powerful, it has some limitations:

Does not protect against other STIs (gonorrhea, chlamydia, syphilis).
Requires strict adherence to daily pills or scheduled injections.
Not suitable for people who already have HIV.
Can cause side effects in rare cases.

Because of these limitations, PrEP should be combined with other HIV prevention methods for the best results.

What to Do If You Think PrEP Can Help You

If you believe PrEP is right for you, follow these steps:

Talk to a healthcare provider about your risk factors.
Get an HIV test before starting. You must be HIV-negative to use PrEP.
Choose your method: daily pills or injections.
Commit to adherence: daily pill-taking or attending regular injection appointments.
Continue prevention practices: use condoms, avoid needle sharing, and get regular STI testing.

Key Takeaways About PrEP

PrEP (Pre-Exposure Prophylaxis) is highly effective at preventing HIV when taken correctly.
Available as daily pills (Truvada, Descovy) or long-acting injections (Apretude, Yeztugo).
Reduces HIV risk from sex by 99% and from injection drug use by at least 74%.
Requires adherence and ongoing medical monitoring.
Does not protect against other STIs—condoms and safer sex practices remain important.

Final Thoughts

PrEP is a safe, powerful, and proven way to prevent HIV infection. Whether you choose daily pills or long-acting injections, PrEP offers protection and peace of mind for people at high risk of HIV. By combining PrEP with other prevention methods such as condom use, regular HIV testing, and safe injection practices, you can significantly lower your chances of HIV infection.

If you think PrEP may be right for you, talk to your healthcare provider today. Acting now can help you take control of your health and protect yourself from HIV.