PrEP Side Effects: What Is Common on Truvada and Descovy, and What Your Kidney and Bone Checks Are For

Worry about side effects stops many people from starting PrEP. The reassuring part comes first: HIV.gov describes PrEP as safe, with no significant health effects seen in HIV-negative people who have taken it for up to 5 years. Some people do get side effects, but they are usually not serious and go away over time¹.

This guide covers the two PrEP pills: Truvada (emtricitabine with tenofovir disoproxil fumarate, or TDF) and Descovy (emtricitabine with tenofovir alafenamide, or TAF), and their generic versions. For the injections, see our guide to the PrEP shot.

Common side effects of Truvada and Descovy

The side effects people mention most are nausea, diarrhoea, headache, tiredness and stomach pain¹.

• Truvada: in the PrEP trials, the side effects reported more often than with a dummy pill were headache, stomach pain and weight loss².
• Descovy: in the large DISCOVER trial, diarrhoea, nausea, headache, tiredness and stomach pain were the most common, at similar rates to Truvada. Fewer than 2 in 100 people stopped either pill because of side effects³.

These early effects usually settle within the first few weeks. The UK guideline notes that taking the first dose with food may reduce stomach upset⁴. Our guide to daily vs on-demand PrEP has more on the first weeks.

Kidneys: what the checks are looking for

Tenofovir is cleared by the kidneys, so kidney checks are part of PrEP. The 2025 UK guideline summarises what the trials found⁴:

• Most people on Truvada-type PrEP have a small drop in kidney function in the first 4 to 12 weeks, which then levels off.
• The vast majority of changes are mild, do not keep getting worse, and are reversible.
• Kidney problems were more likely in people with lower kidney function to begin with, people aged 40 or over, and people with type 2 diabetes, high blood pressure or recreational drug use.

In the US, Truvada is not recommended for PrEP if kidney function (creatinine clearance) is below 60 mL/min². The UK guideline recommends the TAF version (Descovy-type PrEP) for people whose kidney function is between 30 and 60⁴.

How often your kidneys are checked (UK guideline)

Source: BASHH/BHIVA 2025 PrEP guideline⁴. If you take creatine or protein supplements, mention them, because the guideline asks for these to be stopped before a repeat kidney test.

Painkillers matter too. The Truvada label advises avoiding high-dose or multiple anti-inflammatory painkillers (NSAIDs, such as ibuprofen or naproxen) at the same time, because sudden kidney problems have been reported in people with kidney risk factors². Our guide to tenofovir and your kidneys explains kidney tests in more detail.

Bones: a small change that recovers

TDF-based PrEP causes a small drop in bone density. The UK guideline puts the average reduction at less than 2%, with the size of the drop linked to how consistently PrEP is taken, and the rate of loss slowing over time⁴. Three further points from the same guideline:

• After stopping PrEP, bone density has been shown to return to, or close to, where it was before.
• So far there is no evidence of more fractures in people taking TDF-based PrEP.
• The drop appears slightly larger in people aged 25 or under, who are still building bone⁴.

In the DISCOVER trial, bone density rose slightly on Descovy and fell slightly on Truvada³. The UK guideline suggests TAF-based PrEP, or fewer weekly doses, for people with a raised fracture risk, and TAF-based PrEP for people under 18⁴. The Truvada label advises considering a bone scan for people who have had a fracture from a minor injury or have other risks for thin bones².

Weight: Truvada vs Descovy

Weight loss was one of the side effects seen more often with Truvada than with a dummy pill in the PrEP trials². The UK guideline says that TDF tends to hold weight down, so people switching from Truvada-type PrEP to Descovy-type PrEP should be told they may gain a modest amount of weight⁴. Our article on HIV medicines and weight gain explains the difference between the two forms of tenofovir.

The routine tests on PrEP

PrEP comes with regular check-ups. Under the UK guideline⁴:

• HIV test before starting and every 3 to 6 months, and again 45 days after your last risk if you stop.
• STI screening every 3 months if you have new or multiple partners.
• Hepatitis B test at the start, with vaccination if you are not immune. See our guide to PrEP and hepatitis B.
• Hepatitis C testing for people at risk.
• Kidney tests on the schedule above.

In the US, HIV.gov says people on daily PrEP pills see a provider every 3 months for HIV tests, refills and follow-up¹.

When to contact your clinic

• A flu-like illness after a possible exposure, such as a sore throat, high temperature, swollen glands, aches or a rash. Some people get this 2 to 6 weeks after HIV infection⁵, and the UK guideline asks for HIV testing before PrEP is started or continued in that situation⁴.
• Side effects that do not settle after the first few weeks.
• A fracture from a minor fall, or ongoing bone pain.
• If you have hepatitis B and want to stop PrEP. Stopping can cause a flare, so your clinic needs to plan it².

Frequently asked questions

Does PrEP have side effects?

Some people get nausea, diarrhoea, headache, tiredness or stomach pain, usually in the first few weeks. HIV.gov describes PrEP as safe, and in the DISCOVER trial fewer than 2 in 100 people stopped because of side effects.

Does PrEP damage the kidneys?

Most people have a small early dip in kidney function that then levels off and is reversible. Serious kidney problems are uncommon and more likely with existing kidney risk factors, which is why kidney tests are part of PrEP.

Does PrEP cause weight gain?

Truvada-type PrEP tends to hold weight down, and weight loss was seen in the trials. Switching to Descovy-type PrEP may lead to a modest weight gain compared with Truvada, according to the UK guideline.

Do I need blood tests on PrEP?

Yes. You need an HIV test before starting and every few months, kidney tests on a set schedule, a hepatitis B test at the start, and regular STI screening if you have new partners.

Which has fewer side effects, Truvada or Descovy?

Short-term side effects were similar in the DISCOVER trial. Descovy had slightly better kidney and bone test results on average, but Descovy is not approved for people at risk through receptive vaginal sex.

Are there long-term side effects of PrEP?

The ones that are monitored are kidney function and bone density. Both changes are usually small, and bone density has been shown to recover after stopping. There is no evidence so far of more fractures on PrEP.

Sources & references

1. HIV.gov. Pre-Exposure Prophylaxis (PrEP). Updated 9 October 2026.
2. US National Library of Medicine, DailyMed. Truvada prescribing information.
3. US National Library of Medicine, DailyMed. Descovy prescribing information (including DISCOVER trial results).
4. British Association for Sexual Health and HIV and British HIV Association. BASHH/BHIVA guidelines on the use of HIV pre-exposure prophylaxis (PrEP) 2025.
5. NHS. HIV and AIDS: symptoms. Last reviewed 9 July 2025.

Related reading

• PrEP with alcohol, drugs and hormones
• How to get PrEP
• Doxy-PEP for STI prevention
• Truvada vs Descovy
• Starting, missing and stopping PrEP
• Tenvir-EM and Tafmune-EM
• Generic Descovy and our PrEP guide

This content is for informational purposes only and is not medical advice. Your clinic will set your test schedule based on your age, kidney results and other health conditions. Used as prescribed by a licensed medical professional.