PrEP side effects: the full list, by drug & body area

💊 The most common PrEP side effects

When you start PrEP, your body adjusts to a new medicine. About 1 in 10 people notice mild effects in the first weeks — sometimes called "start-up syndrome":

• Nausea or upset stomach — the most common; taking PrEP with food helps. See how to reduce nausea.
• Headache and mild dizziness.
• Tiredness and occasional bloating or loose stools.

Side effects by PrEP medication

PrEP side effects by body area

• Head & brain — headache, mild dizziness early on; usually expected and self-limiting.
• Stomach & gut — nausea, bloating, looser stools; take with food. See reducing nausea.
• Kidneys — tenofovir in Truvada can slightly lower kidney function (checked with routine bloods); TAF and injectables are gentler.
• Bones & joints — Truvada can cause a small, usually reversible drop in bone density; most relevant for older adults.
• Skin — an occasional mild rash is expected; a severe blistering rash or facial swelling is rare and needs urgent care.
• Whole body — tiredness early on; weight/lipid changes linked more to Descovy — see PrEP & weight gain.
• Genitals & urinary — new sores, discharge or pain are almost always an STI, not PrEP — get tested. PrEP doesn't prevent other STIs.

How long do PrEP side effects last?

For most people, early effects fade within 2–4 weeks as the body adjusts. Longer-term, PrEP is considered very safe — the small kidney and bone changes with Truvada are monitored with routine tests and are usually reversible. If a side effect is stubborn, you can often switch (e.g. Truvada → Descovy) rather than stop. Everyday questions:

⚠️ Warning signs that need care

Serious reactions are uncommon, but contact a provider promptly if you notice:

And if you may have been exposed to HIV in the last 72 hours and you're not protected, that's an emergency — see PEP.

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