Truvada is a daily prescription pill (emtricitabine/tenofovir disoproxil fumarate) taken by HIV-negative people to prevent HIV — a strategy called PrEP, or pre-exposure prophylaxis. Taken as prescribed, it lowers the chance of getting HIV from sex by about 99% and from injection drug use by at least 74% CDC PrEP. It only works if you don't already have HIV.
in 2023
≈723,000 — U=U
| Item | Value |
|---|---|
| New diagnoses | 38,800 — in 2023 |
| Living with HIV | 1.12 million |
| Virally suppressed | ~65% — ≈723,000 — U=U |
| On PrEP | 381,000 |
What Truvada and PrEP actually are
PrEP means taking HIV medicine before any exposure so the virus can't establish itself if it gets into your body. Truvada was the first pill approved for this. It combines two antiretroviral drugs that block HIV from copying itself, keeping the virus from taking hold in the first cells it tries to infect.
There are a few oral and long-acting options now. Daily Truvada is approved for everyone at risk through sex or injection drug use. Descovy (emtricitabine/tenofovir alafenamide) is also a daily pill, but it's not approved for people exposed through receptive vaginal sex or for people who inject drugs, because its trials didn't include those groups. There's also a long-acting injectable, cabotegravir (Apretude), given as two starter shots a month apart and then every two months.
PrEP is one piece of HIV prevention, not a vaccine and not a cure. It protects you going forward — it does nothing for an exposure that already happened, and it's separate from hiv treatment, which is for people who already have the virus.
HIV symptoms — and the silent reality PrEP is built around
PrEP exists because HIV is so easy to miss. Within 2 to 4 weeks of infection, about 90% of people develop flu-like symptoms — fever, chills, rash, night sweats, muscle aches, sore throat, fatigue, swollen lymph nodes, and mouth ulcers hiv.gov. This is acute retroviral syndrome, and it lands exactly when the viral load peaks above a million copies/mL, making this the most contagious window.
The problem: those symptoms look identical to the flu, and some people get none at all. After the acute phase, HIV settles into clinical latency — often years with no symptoms while the virus quietly damages the immune system. Symptoms can neither confirm nor rule out HIV. Only a test can, which is why anyone considering PrEP must confirm they're HIV-negative first.
How HIV spreads (and what PrEP guards against)
Only certain body fluids carry HIV: blood, semen, vaginal fluid, rectal fluid, and breast milk CDC. The common routes are anal or vaginal sex, sharing needles or injection equipment, and passing from parent to child during pregnancy, birth, or breastfeeding.
HIV does not spread through saliva, kissing, casual contact, surfaces, food, water, air, insects, or donating blood — it doesn't survive long outside the body. PrEP targets the routes that matter: condomless sex and shared injection equipment. It pairs well with condoms and with treatment-as-prevention, but it doesn't protect against other STIs, so it's not a stand-alone shield.
Testing before and during PrEP
You can't start PrEP with HIV already in your system — that can breed drug resistance. So a confirmed negative test comes first, plus baseline kidney-function, hepatitis B, and STI screening CDC testing. Testing then continues every 3 months on oral PrEP, or every 2 months on the injectable.
Testing itself is quick — a finger-stick or oral-swab rapid test gives results in minutes, and lab blood tests are widely available. Many health departments offer it free, and at-home kits exist. The catch is the window period: a test only counts after enough time has passed since the last exposure.
- Nucleic-acid test (NAT): 10–33 days after exposure.
- Antigen/antibody (4th-gen) lab test: 18–45 days.
- Antibody/rapid tests: 23–90 days.
A negative result is conclusive only after the window closes with no exposure during it. If the timing is confusing, read when to test after exposure before you book — and when you're ready, get tested or compare testing providers to find an option that fits.
How well PrEP works
PrEP's protection tracks closely with how consistently you take it. In the iPrEx trial, daily pills cut HIV risk about 44% overall but roughly 92% among people who actually took the medicine. On-demand "2-1-1" dosing reached 86% in IPERGAY, and the long-acting cabotegravir shot beat daily pills by 66% in HPTN 083.
Newer options keep raising the bar. The twice-yearly injectable lenacapavir produced zero infections among women in the PURPOSE 1 trial — the strongest HIV-prevention result recorded to date WHO. The lesson across all of these: adherence and method choice are what turn PrEP into near-complete protection.
| Option | How it's taken | Approved exposure routes |
|---|---|---|
| Truvada (daily oral) | One pill daily | Sex (all) and injection drug use |
| Descovy (daily oral) | One pill daily | Not for receptive vaginal sex or injection drug use |
| Cabotegravir / Apretude | Two starter shots a month apart, then every 2 months | Sex and injection drug use |
If you might have already been exposed: PEP, not PrEP
PrEP is for ongoing protection — it can't undo an exposure that already happened. For that, there's PEP (post-exposure prophylaxis): a 28-day course that must start within 72 hours of a possible exposure CDC PEP. In the original occupational study, prompt PEP cut HIV seroconversion by about 81%.
PEP is an emergency — an urgent-care or ER conversation, not a wait-and-test one. The sooner it starts, the better it works. Once the immediate risk is handled, PrEP is what protects you going forward.
What HIV does if it's not prevented or treated
Untreated HIV progresses through chronic latency to AIDS — defined by a CD4 count under 200 cells/mm³ or an opportunistic infection (illnesses that take hold when the immune system can no longer defend the body) CDC. AIDS is the most severe, life-threatening stage.
There's no cure: latent HIV hides in reservoirs of cells and rebounds if treatment stops, so even an undetectable viral load is control, not eradication HHS clinicalinfo. But modern care changes the outlook dramatically — a 20-year-old who starts treatment before their CD4 falls below 200 now has a life expectancy approaching the general population's Lancet HIV. That's the whole case for prevention and early testing.
PrEP within the full prevention toolkit
The CDC's core prevention tools are condoms, PrEP, PEP, treatment-as-prevention (U=U), and regular testing. PrEP is the only one you take when you're HIV-negative and want forward protection — but it works best layered with the others, since it doesn't cover other STIs.
On the treatment side, U=U is the headline: someone with HIV who takes their medicine and stays virally suppressed (undetectable) does not transmit HIV to sex partners. Across the PARTNER, Opposites Attract, and PARTNER2 studies — more than 125,000 condomless sex acts — there were zero linked transmissions while partners were undetectable PARTNER study. Treatment is both health and prevention.
Perinatal transmission is also preventable: with treatment during pregnancy and labor plus newborn prophylaxis, the risk of passing HIV to a baby can drop to less than 1% CDC. If this applies to you, see hiv & getting pregnant and is early hiv treatment in babies safe and effective.
When to see a clinician
The USPSTF gives HIV screening a Grade A recommendation: everyone ages 15–65 should be screened at least once, with repeat testing at least annually for those at increased risk USPSTF. If you have ongoing risk through sex or injection drug use, that's the conversation to start about PrEP.
- You had a possible exposure in the last 72 hours — seek PEP urgently, same day.
- You have flu-like symptoms 2 to 4 weeks after a risk — ask for an urgent test, since this is the most contagious window.
- You're HIV-negative but have ongoing exposure risk — ask about starting PrEP and the testing schedule that goes with it.
- You're on PrEP — keep your follow-up visits, since regular testing and kidney checks are part of staying on it safely.