The claim that will not die

“Creatine is hard on your kidneys.” “It’s fine short-term, but long-term use isn’t studied.” “Endurance athletes shouldn’t take it — it’s for strength sports.” If you have competed in endurance sport for any length of time, you have heard some version of these claims. Possibly from a training partner. Possibly from a well-meaning coach. Possibly from a blog post citing a study from the 1990s that looked at a single case report.

These concerns have persisted in the endurance community for decades. They’re worth revisiting, because the evidence base on creatine monohydrate safety has grown considerably — and a structured analysis published in Sports in April 2026 represents one of the most comprehensive reviews to date of whether creatine dose and duration actually drive side effects.

In this article, we’ll walk through what the 2026 review analyzed, what it actually found, the limits and caveats of the data, and how the safety conversation relates to — and differs from — the efficacy conversation for endurance athletes specifically. The aim is to give you an honest, hedged read on what the current literature supports. Not a sales pitch for creatine. Not a blanket endorsement. A clearer view of what the evidence actually says.

Why the safety question matters — and why it keeps resurfacing

Creatine is one of the most-studied nutritional ergogenic aids in sport science. It has been researched since the 1970s, with more than 650 peer-reviewed clinical trials on creatine monohydrate specifically by the time of the 2026 review (Gonzalez et al., 2026). That is a deep evidence base by the standards of any supplement.

But popular understanding of creatine hasn’t always kept pace with the research. The “creatine is hard on your kidneys” concern originated largely from a 1998 case report of a single patient with pre-existing renal disease — a report that has been cited widely, often without the context that subsequent controlled research in healthy populations has not replicated the kidney-function concerns the case report raised (Kreider et al., 2017).

Concerns about long-term use persisted in part because, for years, long-term controlled data was limited. That has changed. The 2026 structured review now includes trials with durations running up to 14 years, across diverse populations, with the specific goal of examining whether dose or duration predicts side effects (Gonzalez et al., 2026).

The review is worth reading carefully not because it’s the final word — no single paper ever is — but because it’s one of the most comprehensive looks at the safety question to date, and it directly addresses the dose- and duration-specific concerns that have historically driven the “I’m not sure about creatine” position in the endurance community.

What the 2026 review actually analyzed

Gonzalez and colleagues conducted a PubMed-based comprehensive literature search using the terms “creatine” and “supplementation,” then filtered to include only randomized controlled trials in humans on creatine monohydrate. Animal studies, literature reviews, meta-analyses, patents, and unrelated publications were excluded. The result was 685 randomized controlled clinical trials that met inclusion criteria, covering data from 12,800+ participants across the creatine and placebo arms (Gonzalez et al., 2026).

For each trial, the researchers extracted:

• Sample size per study arm
• Study design and intervention duration
• Absolute and body-mass-adjusted creatine dose
• Participant demographics (including sex and age group)
• Training status (clinical populations, untrained, recreationally active, trained/athletic, military)
• Health status (healthy vs. clinical)
• Reported side effects, categorized into 35 standardized indicators (coded yes/no for each trial)

Total creatine exposure (grams) and total supplementation duration (days) were then divided into tertiles — low, moderate, and high exposure — and analyzed for side-effect prevalence using chi-square testing and logistic regression models adjusted for sex, age group, population category, and health status (Gonzalez et al., 2026).

Three model sets were used: a covariates-only model, a dose- and duration-adjusted model, and a tertile-only sensitivity model. This approach was specifically designed to test whether exposure level predicted side-effect reporting, rather than simply whether side effects occurred.

What the safety data actually showed

Across the 685 analyzed trials:

• Reported side effects were infrequent, mild, and nonspecific.
• Although some dose and duration tertiles were statistically associated with whether side effects were reported at the study level, effect sizes were uniformly small, and the pattern was not consistent across physiological systems or exposure categories.
• No consistent exposure–response pattern indicative of clinically meaningful risk was observed.
• Placebo groups often reported similar or greater side-effect frequencies compared with creatine groups at the study-reporting level.
• These findings held across gastrointestinal, renal, liver, musculoskeletal, and other side-effect categories (Gonzalez et al., 2026).

In short: looking across 685 RCTs covering doses up to 30 g/day and durations up to 14 years, the review found no consistent signal that higher creatine exposure — whether through larger daily doses or longer durations — was associated with more side effects than placebo in healthy populations.

The authors note that this aligns with earlier safety conclusions from the International Society of Sports Nutrition position stand on creatine (Kreider et al., 2017), which has been updated multiple times as the evidence base has grown and has consistently concluded that creatine monohydrate is well-tolerated in healthy adults under the doses and durations commonly studied.

The 2026 review also cites additional data from pharmacovigilance reporting systems. Analysis of more than 28 million side-effect reports from the United States, Canada, Australia, and Europe over 50 years using SIDER 4.1 shows creatine mentioned in only approximately 0.0007% of reports, despite what the authors describe as billions of doses administered globally over the last 30 years. Pharmacovigilance data cannot establish causality and is subject to reporting biases, but the near-absence of creatine-associated reports is consistent with the clinical trial findings (Gonzalez et al., 2026).

Important caveats — where the nuance lives

No single study — even a structured review of 685 trials — closes any conversation completely. The authors themselves name several limits of the analysis, and it’s worth sitting with them before drawing conclusions.

This is study-level, not participant-level, data

The analysis asks: across these 685 trials, how often did studies in each exposure tertile report any side effect? It does not track individual participant outcomes in a pooled meta-analysis sense. That means the conclusions describe reporting patterns across studies, not individual-level risk estimates. For most practical purposes, the two align — the reporting pattern is what you’d expect if individual risk were also low — but the distinction should be stated (Gonzalez et al., 2026).

The safety signal is strongest in healthy populations

The majority of the trials included healthy adults and athletic populations. Clinical populations were represented but were a smaller share. Individuals with pre-existing renal disease, liver disease, or chronic conditions affecting metabolism have a different baseline risk profile, and the general safety conclusions may not apply directly to them (Gonzalez et al., 2026; Kreider et al., 2017).

Pregnancy, lactation, and children are separate conversations

The review does include data from pediatric trials, but the specific risk-benefit calculation for pregnancy and lactation is something most practitioners handle conservatively, even in the absence of a clear safety signal. If you are pregnant, trying to become pregnant, or lactating, talk to your clinician before starting creatine — that is the standard conservative position, and it is appropriate here.

Medication interactions are not fully characterized

If you take medications that affect kidney function — such as certain NSAIDs used chronically, some diuretics, or medications that alter creatinine metabolism — the interaction picture is less thoroughly studied than the baseline safety profile in healthy adults. This is another reason to check with your clinician if you’re on chronic medication.

“Absence of harm” is not the same as “harm-free”

This is a methodological point worth internalizing. Well-replicated safety data in a large sample is the strongest evidence a reasonable person can hope for, and it does not logically prove that no individual will ever experience any adverse effect. Some individuals have idiosyncratic responses to any supplement. The population-level safety signal is reassuring. It is not a guarantee.

Safety and performance are two different conversations

One of the most important distinctions in the creatine literature — and one that often gets blurred — is between the safety evidence and the efficacy evidence.

The safety question asks: does creatine cause harm? The 2026 review addresses this question directly, and the answer in healthy adults, at the doses and durations studied, is essentially “no consistent signal of harm.”

The efficacy question asks: does creatine make me faster, stronger, or better able to recover? The answer there depends heavily on what you’re trying to do, and it is genuinely more nuanced — particularly for endurance athletes.

Mixing these two conversations is how athletes end up either writing off a reasonably well-established safety profile on speculative grounds, or expecting performance benefits in their specific sport that the evidence doesn’t fully support.

Where creatine may — and may not — help endurance athletes

The performance case for creatine is strongest in sports and efforts that rely heavily on the phosphocreatine (PCr) energy system: short, high-output actions where rapid ATP resynthesis determines repeatability. Strength training. Sprinting. Jumping. Repeated high-intensity efforts with short recoveries (Kreider et al., 2017).

Most endurance racing isn’t primarily PCr-dependent. A marathon, a 70.3, a gravel century, an ultramarathon — the bulk of the energy comes from aerobic metabolism of carbohydrate and fat. You wouldn’t expect creatine to directly improve aerobic capacity or sustained race-pace output, and the evidence base for that effect is genuinely mixed (Kreider et al., 2017).

That said, several contexts relevant to endurance athletes are worth naming:

1. Strength work that supports durability

Many competitive endurance athletes include a structured strength component — and for good reason. Strength training supports injury resistance, movement economy, and late-race durability, particularly in longer events. In the strength context, creatine’s evidence base is strong: it supports improvements in strength, power, and training capacity (Kreider et al., 2017). If you’re doing a strength block, creatine may amplify the adaptations from that block.

2. High-intensity interval training and repeat-sprint efforts

HIIT sessions, whether on the bike or on the run, rely on repeated high-output efforts with incomplete recovery. The PCr system matters here. Evidence on creatine’s role in supporting these specific session types within an endurance block suggests potential context-dependent benefits, though sport-specific effect sizes vary (Kreider et al., 2017).

3. Recovery between hard sessions

There is research suggesting creatine may support recovery between high-intensity sessions, particularly under heavy training loads. This is where creatine’s practical value for endurance athletes may be most defensible — not in making a race day faster, but in enabling more consistent weekly training quality (Kreider et al., 2017).

4. Muscle mass preservation with age

For the 30–55-year-old endurance athlete — the demographic I spend most of my time working with — age-related changes in muscle mass and quality start to become relevant. Creatine has been studied extensively in the context of muscle mass maintenance in older adults, and the ISSN position stand lists this among its established applications (Kreider et al., 2017). Masters-age endurance athletes who want to support durability and trainability as they age may find this reason alone worth considering.

Where the evidence doesn’t support expecting a benefit

Don’t expect a race-day bump in pure aerobic endurance performance. The evidence for that is mixed, and in many studies, effects are null or small (Kreider et al., 2017). If someone is telling you creatine will give you a marathon PR, the evidence isn’t really there for that specific claim.

The IOC framing

For context, the International Olympic Committee consensus on dietary supplements and high-performance athletes lists creatine as one of a small number of supplements with direct performance evidence in specific contexts — alongside caffeine, beta-alanine, sodium bicarbonate, and nitrate (Maughan et al., 2018). That’s a short, carefully-vetted list. Being on it is meaningful. It also means creatine is on the “worth considering in appropriate contexts” list, not the “everyone should take everything” list.

Practical framing for endurance athletes

If you’ve read this far, a few practical considerations are worth naming.

Supplements are never the first lever. Your nutrition, training distribution, sleep, and recovery will move your performance numbers far more than any supplement on any list. If you’re under-fueled, under-slept, or structurally over-trained, the right answer is to fix those first. Creatine will not rescue an incoherent training plan.

Creatine monohydrate, not exotic forms. The safety and efficacy evidence is specifically strongest for creatine monohydrate (CrM) — the form studied in the 685 RCTs the review analyzed (Gonzalez et al., 2026). Novel forms like creatine ethyl ester, creatine HCl, and others are marketed with claims of superiority, but the evidence base supporting those claims is considerably weaker (Kreider et al., 2017). Monohydrate is the standard, and it’s also the cheapest.

Dose protocols. The ISSN position stand describes two common approaches (Kreider et al., 2017):

• Loading approach: Approximately 20 g/day split into four doses (5 g each) for 5–7 days, then approximately 3–5 g/day maintenance.
• No-loading approach: Approximately 3–5 g/day from the start, without a loading phase. This approach reaches saturation more gradually — typically over 3–4 weeks — but avoids the temporary water-weight bump from loading.

For weight-sensitive endurance athletes, the no-loading approach is often the more practical option, because it avoids the ~0.5–1.5 kg body-mass increase typical of loading (Kreider et al., 2017). Timing around key races is a separate question — some athletes prefer to hold off on initiating creatine in the final 4–6 weeks before a weight-sensitive event, not on safety grounds, but because they don’t want to introduce any new variable close to competition.

Quality matters. Supplement quality varies, and athletes subject to sport-specific anti-doping testing should consider third-party-tested products (Informed Sport, NSF Certified for Sport) to reduce the risk of contamination. The IOC consensus on supplements notes contamination risk as a real consideration for high-performance athletes (Maughan et al., 2018).

Population matters. The safety conclusions in the 2026 review are strongest in healthy adults. If you have a history of kidney disease, are on chronic medication, are pregnant or trying to become pregnant, or have any condition that affects fluid balance or metabolism, this is a clinician conversation — not a content-marketing conversation.

Frequently asked questions

Work with Kyla and the Nutritional Revolution team

Supplementation is one of the smaller levers in a well-designed sports nutrition program. The bigger levers — daily fueling that matches your training load, race-week protocols built on current evidence, sweat testing, lab work review, and periodized nutrition that actually updates as the season changes — are where most of the progress happens.

At Nutritional Revolution, we work with competitive endurance athletes 1:1 and in small group cohorts to build that infrastructure. If you want to stop guessing and start operating from a plan grounded in current peer-reviewed evidence, we’d like to talk.

References

About Kyla Channell, MS

Kyla Channell, MS, is a sports nutritionist specializing in high-performing endurance athletes. She holds a Master of Science in Nutrition and Human Performance (graduated with high distinction), an International Olympic Committee Sports Nutrition Diploma, and a Bachelor of Science in Clinical Dietetics from UC Davis. At Nutritional Revolution, Kyla consults with competitive endurance athletes — cyclists, ultrarunners, triathletes — designing customized nutrition programming grounded in current peer-reviewed sports science. Her practice integrates sweat testing, laboratory work review, and periodized fueling strategies so athletes can perform at their highest level.