Safety · CREA-SAFE-01 · v2
The question is whether taking creatine harms the kidneys in healthy people. The most direct trials in healthy adults looked for signs of harm and did not find them: one measured kidney filtration directly over 12 weeks and saw no change [2], and another tracked sensitive markers of kidney injury over 35 days and saw no rise [5]. One small athlete study did find a rise in blood creatinine and urea, but the levels stayed within the normal range and this is what you would expect because the body turns creatine into creatinine [7]. A study in patients with artery disease also found no effect on kidney function [6]. The panel concluded the corpus does not show the harm the claim describes, while noting the trials are small and short, so long-term or very-high-dose use remains untested.
The directly relevant healthy-adult trials point away from impairment. In resistance-trained adults on a high-protein diet, directly-measured glomerular filtration rate by 51Cr-EDTA clearance did not change over 12 weeks [2], and creatinine clearance, urea, electrolytes and proteinuria stayed virtually unchanged [2]. In young healthy male students, sensitive injury biomarkers KIM-1 and MCP-1 were not elevated after 35 days, and the serum creatinine rise seen on supplementation stayed within the normal reference range and is attributed to creatine metabolism [5]. The one significant rise in blood urea and creatinine [7] was explicitly bounded within normal limits. A trial in peripheral artery disease patients likewise found no change in creatinine clearance [6]. The contested point: The only within-corpus tension is how to read the significant creatinine and urea rise in [7]: it is statistically significant yet stays within normal limits, and serum creatinine is a by-product of creatine metabolism rather than a clean filtration marker [5]. The panel read this as metabolic indirectness, not demonstrated renal injury.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
[7] reports a statistically significant rise in blood urea and creatinine, which could superficially support impairment; but serum creatinine is a confounded marker in creatine users because exogenous creatine elevates serum creatinine independently of filtration, and the paper bounds the rise within normal limits — indirectness, not demonstrated impairment.
All included trials are small ([5] N=36, [6] N=29, [7] N=12) and short (35 days to 12 weeks); the corpus cannot address long-term or supraphysiological-dose chronic use.
Where it remains uncertain. One athlete study found a significant creatinine and urea rise [7], but it remained within normal limits and reflects creatine being metabolised to creatinine [5].
Aleatory
Participant counts are low ([5] N=36, [6] N=29, [7] N=12), so random variation could obscure a small true effect.
Epistemic
Follow-up spans 35 days to 12 weeks; chronic and supraphysiological-dose use is untested in the corpus.
Inferential
Exogenous creatine raises serum creatinine independently of filtration [5], so a rise in [7] cannot be read as impairment.
The load-bearing papers from a corpus of 10, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
The only included paper with a significant biomarker rise; bounds it within normal limits, consistent with a metabolic artifact rather than impairment.
“Although there were increases in urea and creatinine levels in the blood, the amount was still within normal limits.”
Panel auditInternal validity: low · scope of inference: Healthy dragon boat athletes, 5-week high-dose creatine.Key limitations: very small sample · creatinine confounded by creatine metabolism · values remained within normal limits · no GFR measure
Gold-standard directly-measured GFR (51Cr-EDTA) unchanged in healthy adults — directly refutes impairment.
“A 12-week creatine supplementation protocol did not affect kidney function in resistance-trained healthy individuals consuming a high-protein diet; thus reinforcing the safety of this dietary supplement.”
Panel auditInternal validity: high · scope of inference: Healthy resistance-trained adults on a high-protein diet, 12-week creatine exposure.Key limitations: total sample size not stated in abstract · 12-week duration only
Supporting context (population drift to PAD patients); no renal compromise, weighted low.
“Eight weeks of creatine supplementation is safe and does not compromise the renal function of patients with peripheral arterial disease.”
Panel auditInternal validity: medium · scope of inference: Patients with symptomatic peripheral arterial disease, 8-week creatine exposure.Key limitations: not healthy adults · small sample · creatinine-based measures only
3 of 10 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
Across the included primary trials in healthy adults, no measure of actual renal function was impaired, so the claim of impairment is not carried by the corpus.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Long-term and high-dose chronic use. All included trials run 35 days to 12 weeks, so cumulative or supraphysiological-dose effects on the kidney are unaddressed. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A multi-year RCT in healthy adults on maintenance creatine with periodic directly-measured GFR and injury biomarkers.
Open question: Does chronic, multi-year creatine use affect directly-measured kidney function in healthy adults? Why it is still open: All included trials end by 12 weeks [2] and cannot speak to long-term use.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 21 Oct 2026 · protocol v0.19