Is creatine bad for your kidneys?

In 2017 the International Society of Sports Nutrition (ISSN) reviewed the accumulated evidence and concluded that creatine monohydrate is safe for healthy people at recommended doses — including years of continuous use. The review found no evidence that creatine harms the kidneys, the liver, or hydration in healthy adults.

One detail explains much of the worry: creatine breaks down into creatinine, the exact marker doctors measure in blood tests to assess kidney function. Someone taking creatine can therefore show a slightly elevated creatinine value without any change in kidney health — the number rises because more creatine is being turned over, not because filtration got worse.

The important caveat: the evidence is strongest for healthy people. With existing kidney disease the data is thinner, and that decision belongs with a doctor.

Three mechanisms keep the myth alive. Creatine raises the creatinine value in blood tests — the same number used to screen kidney function — so a completely harmless test result can look like a warning sign, even to clinicians who don't know the patient takes creatine. Creatine has also been found guilty by association: it sits on the same shelves and in the same tubs as far more questionable products, and inherited their reputation. And a handful of case reports about people with already impaired kidneys made headlines, while the controlled studies clearing creatine never became news.

3–5 g of creatine monohydrate a day is enough — a loading phase is optional and only changes how fast your stores fill. Take it whenever it suits you; timing matters little. If you have kidney disease or take medication that affects the kidneys, talk to a doctor first. And tell your clinician you take creatine if your creatinine value is being interpreted.