Is creatine bad for your kidneys?

No — not in healthy adults. No controlled trial has ever found that creatine impairs kidney function, including the trials that measured filtration directly instead of estimating it.

The strongest evidence is a 2025 meta-analysis in BMC Nephrology and a 2013 double-blind RCT that measured glomerular filtration rate with a 51Cr-EDTA tracer — the gold standard — in resistance-trained men already eating a high-protein diet, the exact scenario the worry is usually about. Twelve weeks of creatine changed nothing.

Why the myth is so sticky

Creatine constantly breaks down into creatinine, which happens to be the blood marker doctors use to estimate kidney function. Take creatine and your creatinine goes up — not because your kidneys are filtering worse, but because you are producing more of the very thing being measured.

A 2014 BMJ Case Reports paper captures it perfectly: a bodybuilder's creatinine climbed to nearly twice the normal range, and fell straight back to normal when he stopped the supplement. His kidneys were fine the whole time. The practical lesson — if you get a blood test, tell your doctor you take creatine.

The honest caveats

• There is one published case of biopsy-confirmed kidney inflammation attributed to creatine. It is counted in the evidence below rather than quietly dropped.
• Two other case reports often cited alongside it are confounded — one of those patients had pre-existing kidney disease and five years of a known kidney-toxic drug.
• Against three case reports stand multiple controlled trials that found nothing.

One genuine gap remains, and the researchers themselves flag it: people who already have kidney disease have not been properly studied. If that is you, this answer does not apply — ask your doctor.