Is PrEP Bad for Your Kidneys? A Look at the Risks

TDF-based PrEP causes a small, measurable dip in kidney function, but for the vast majority of users it is modest, does not get worse over time, and reverses once the medication stops. Across randomized trials, the average decline amounts to roughly 2 to 3 mL/min in estimated kidney filtration rate compared with placebo. That is a fraction of the natural variation your kidneys experience day to day. The picture gets more interesting when you look at who is most affected, what newer formulations do differently, and how monitoring catches the rare person who needs to stop.

How Large Is the Actual Kidney Effect

In the Partners PrEP trial, one of the largest randomized studies of TDF-based PrEP, people taking the active drug had an average estimated glomerular filtration rate (eGFR) about 2 to 3 mL/min lower than those on placebo at their last visit while still on the medication. To put that in context, a healthy young adult typically has an eGFR well above 100 mL/min, so a 2 to 3 point shift is tiny in absolute terms.¹ A separate systematic review and meta-analysis pooling both trial and real-world implementation data found that PrEP users had about 1.5 times the odds of a mild (grade 1 or higher) kidney event compared with controls, though more serious events (grade 2 and above) were rare and the association was not statistically significant for those more severe outcomes.²

In the iPrEx trial of men who have sex with men, the pattern was similar. Researchers saw a small but statistically significant decrease in creatinine clearance starting as early as the fourth week, but the decline did not get progressively worse over time. The net difference between the active drug and placebo arms persisted while people took the medication and then disappeared once they stopped.³ The word “nonprogressive” keeps appearing across these studies, and it matters. Your kidneys do not keep losing function the longer you stay on PrEP; the dip happens early and then levels off.

Why TDF Affects the Kidneys at All

The kidney effect traces to how tenofovir disoproxil fumarate (TDF) is processed. After you swallow the pill, TDF converts into tenofovir in the bloodstream, and the kidneys are tasked with filtering it out. Tenofovir concentrates in the proximal tubules, the part of the kidney responsible for reclaiming useful molecules from urine. At high enough local concentrations, the drug interferes with the energy-producing machinery inside those cells. Animal studies have shown that TDF disrupts mitochondrial function in the proximal tubules, reducing the activity of several key enzyme complexes involved in generating cellular energy. When those mitochondria underperform, the tubular cells cannot do their job as efficiently, leading to the measurable but usually mild changes in filtration that show up on blood tests.⁴

This mechanism also explains why the effect reverses. Once TDF is out of the system, the tubular cells are no longer being exposed to the drug, mitochondrial function recovers, and kidney filtration returns to where it was. In rare cases, people develop a more serious condition called Fanconi syndrome, where the proximal tubules start leaking substances that should be reabsorbed. In the large DISCOVER trial comparing TDF-based and TAF-based PrEP, Fanconi syndrome was reported in just one participant on TDF and none on TAF.⁵

Who Faces Higher Risk

Not everyone’s kidneys respond the same way. Two factors consistently predict larger declines in kidney function while on TDF-based PrEP: older age and the kidney function you start with.

In a large observational cohort from southern Africa, creatinine clearance declined about 2.6% over time in people who started PrEP before age 40. For those who started between 40 and 50, the decline was roughly 4.2%, and for those 50 and older it reached about 4.9%. In the same analysis, baseline creatinine clearance and age were the only factors that held up in a multivariate model that also accounted for hypertension, body mass index, and recent painkiller use.⁶ A separate observational study confirmed that rates of sustained kidney impairment were lower in people under 40 than in older age groups, and that PrEP users still fared better than people living with HIV on the same drug.⁷

The meta-analysis in The Lancet HIV broke this down further using individual participant data. Among more than 14,000 PrEP users followed over time, about 2.4% experienced a decline to below 60 mL/min creatinine clearance, a threshold that signals meaningful impairment. The risk was dramatically higher for people who started with already borderline function (60 to 90 mL/min) or with function already below 60.² This is the strongest argument for the blood test you get before starting PrEP: if your kidneys are already working at reduced capacity, TDF can push them further in a way that is harder to absorb.

Does Kidney Function Actually Bounce Back

Yes, and the data here are reassuring. In the Partners PrEP trial, eGFR values were essentially identical across TDF, combination, and placebo groups within four weeks of stopping the study drug. By eight weeks, more than 96% of participants had returned to at least 75% of their baseline kidney function, and by twelve weeks that figure was 100%.¹ The iPrEx trial showed the same pattern: after stopping, the mean difference in creatinine clearance between the drug and placebo arms vanished entirely.³

The fact that recovery is so consistent reinforces a useful way to think about this: TDF-based PrEP does not damage your kidneys the way, say, uncontrolled diabetes or severe high blood pressure damages them over decades. It puts a mild, reversible stress on one part of the kidney. When the stress goes away, the kidney goes back to normal. That said, the very long-term picture (think decades of continuous daily use) remains understudied. Most trial data cover periods of one to five years, and the real-world cohorts that span longer tend to see people cycling on and off PrEP rather than taking it uninterrupted.

How Kidney Monitoring Works on PrEP

Every clinical guideline for TDF-based PrEP includes regular kidney function checks. In the United States, the CDC recommends testing every six months. The World Health Organization recommends quarterly monitoring during the first year and then annually after that.⁸ These tests look at serum creatinine, from which your provider calculates an estimated clearance rate.

How often do problems actually surface? In clinical trials using quarterly monitoring, about 1.4% of participants showed a creatinine clearance below 60 mL/min at the first three-month check, but fewer than a quarter of those were confirmed upon repeat testing. By twelve months, the confirmed rate was 0.7%. In a study using six-monthly monitoring, the confirmed rate was even lower: about 0.2% at both the six- and twelve-month marks.⁸ In practice, a real-world Australian clinic reported discontinuing PrEP for kidney concerns in just 2 out of about 500 patients, a rate of 0.4%.⁹

None of the current guidelines recommend more aggressive screening for people with specific risk factors like older age or borderline kidney function. Whether that should change is an open question. The data suggest those groups are where most of the kidney events cluster, so a case can be made for tighter monitoring in people over 50 or those who start with creatinine clearance in the 60 to 90 range, even if formal guidelines have not caught up yet.

TAF-Based PrEP and the Kidney Advantage

Tenofovir alafenamide (TAF) is a newer prodrug of tenofovir that reaches the target cells (immune cells where HIV would replicate) more efficiently, meaning less tenofovir ends up circulating through the blood and filtering through the kidneys. This translates into a measurable kidney benefit. A large meta-analysis covering 24 randomized trials and nearly 22,000 participants found that TAF-based regimens were associated with an eGFR about 3.7 mL/min higher than TDF-based regimens from the start of treatment.¹⁰

The DISCOVER trial, which directly compared TAF-based and TDF-based PrEP in men who have sex with men and transgender women, reinforced this. Participants on TDF had more treatment-emergent proteinuria (protein leaking into the urine, a sign of tubular stress) than those on TAF, and more of them had elevated urine protein-to-creatinine ratios. Renal adverse events leading to discontinuation were also numerically fewer in the TAF group. When people who had been taking TDF-based PrEP before the trial were randomized to switch to TAF, their kidney filtration improved as early as four weeks after the switch.⁵

TAF is not without trade-offs. It tends to cause more weight gain and less favorable changes in lipid profiles compared with TDF, so the choice between the two is not simply “newer equals better.” But for people whose kidney function is a particular concern, TAF offers a clear advantage on that specific front. Your provider can help weigh the full picture.

Event-Driven Dosing and Less Kidney Exposure

Daily PrEP is not the only option for some populations. Event-driven (or “on-demand”) PrEP involves taking pills around the time of potential exposure rather than every single day. Because total drug exposure is lower, you would expect less kidney impact, and a five-year cohort study supports that expectation. Daily users in that study experienced a statistically significant eGFR decline of about 0.57 mL/min per year, while event-driven users showed no significant decline at all.¹¹ Even the daily decline was quite small in absolute terms, but the absence of any measurable effect with on-demand dosing is noteworthy.

Event-driven PrEP is currently recommended mainly for cisgender men who have sex with men and is used more widely in Europe than in the United States. It is not validated for other populations such as cisgender women or people who inject drugs, largely because the pharmacokinetics of tenofovir differ by tissue type. Still, for those who qualify, it offers a way to get effective HIV prevention with even less kidney exposure than daily pills.

Injectable Cabotegravir as a Non-Tenofovir Option

Long-acting injectable cabotegravir (brand name Apretude) sidesteps the kidney question almost entirely because it is not a tenofovir-based drug. It works through a completely different mechanism and does not concentrate in the proximal tubules. A meta-analysis comparing long-acting cabotegravir with oral TDF-based PrEP found that cabotegravir was associated with a lower risk of decreased creatinine clearance.¹² It also turned out to be more effective at preventing HIV infection in the trials, though it comes with injection-site reactions that some people find unpleasant and requires visits to a clinic every two months.

For someone with pre-existing kidney disease who might otherwise be excluded from TDF-based PrEP, injectable cabotegravir is an especially attractive alternative. The same goes for anyone who has had a confirmed kidney decline on oral PrEP and still needs prevention. The landscape of PrEP options has expanded enough that kidney concerns no longer need to mean going without protection.

Adolescents and Young Adults

Most of the kidney data come from adults in their twenties through forties, so the question of whether PrEP is safe for younger users deserves a separate look. Current evidence suggests that PrEP is safe for adolescents, but researchers have noted that the long-term effects on kidney function in this age group remain understudied. Because adolescents are still growing and their kidney function baseline is different from that of older adults, there is an understandable caution about extrapolating too freely from adult trial data. Ongoing studies are working to fill this gap, and existing guidelines do allow PrEP prescribing for adolescents at substantial risk of HIV.

Kidney Screening in Pregnancy

Pregnancy itself changes kidney function dramatically. Creatinine clearance increases by roughly 35% or more during the second and third trimesters compared with six months after delivery, and serum creatinine drops accordingly.¹³ This creates a practical challenge: the thresholds clinicians use to decide whether someone’s kidneys can handle TDF were developed using nonpregnant values. A creatinine clearance that looks normal in pregnancy might actually mask a problem that becomes apparent postpartum, and a value that looks low might just reflect the body’s shifted baseline.

Because of this, screening for kidney function has become a routine step before starting TDF-containing PrEP or antiretroviral treatment in pregnant women. The issue is not that pregnancy makes TDF more dangerous to the kidneys per se, but that interpreting kidney tests accurately during pregnancy requires pregnancy-specific reference ranges, and those ranges have only recently been established for African populations where PrEP use in pregnancy is most common. Getting this right matters: underestimating kidney function could deny a pregnant woman effective HIV prevention she actually needs, while overestimating it could expose her kidneys to a drug they cannot handle well.

When to Be More Careful and When to Relax

If you are under 40, have healthy kidneys at baseline, and are using PrEP under standard monitoring, the kidney risk is about as close to negligible as a drug side effect gets. The measurable decline is small, does not worsen over years, and resolves after stopping. For most people, the bigger risk equation is not kidney function but HIV acquisition: the consequences of unprotected exposure to HIV far outweigh the mild, reversible kidney stress of PrEP.

The situations where you and your provider should pay closer attention include starting PrEP over age 50, already having a creatinine clearance in the 60 to 90 range, or taking other medications that also stress the kidneys. In those cases, more frequent monitoring, a switch to TAF-based PrEP, or a conversation about injectable cabotegravir are all reasonable options. If a blood test ever shows your kidney function dipping below the safety threshold, stopping TDF-based PrEP and rechecking in a few weeks will almost certainly show recovery. The drug interruption rate triggered by kidney-related abnormalities in the Partners PrEP trial was about 1.2% of all participants across both active arms and placebo combined, and median time to the first such interruption was 12 months.¹ In other words, even the “problems” are caught early and resolve cleanly.

One misconception worth addressing directly: some people hear that PrEP affects the kidneys and assume the damage is similar to what happens in chronic kidney disease from diabetes or hypertension. Those conditions cause structural scarring that does not reverse. TDF-based PrEP causes a functional change driven by mitochondrial stress in one segment of the kidney, and function comes back when the drug clears. These are fundamentally different situations, and conflating them leads to unnecessary fear about a medication that prevents a life-altering infection.