Is creatine safe for men over 40?

Creatine monohydrate at 3–5 g/day is safe for healthy men over 40 without pre-existing kidney disease, more than 500 peer-reviewed trials have evaluated it, and a complete systematic review found no evidence of kidney function decline, liver dysfunction, or any serious adverse event in healthy adults at standard doses (Antonio & Ciccone, J Int Soc Sports Nutr, 2013).

The kidney safety concern persists in popular discourse because creatine supplementation raises serum creatinine, a marker used to estimate kidney filtration rate, without actually impairing kidney function. Creatinine is a metabolic byproduct of creatine metabolism; more creatine in the body means more creatinine in the blood, which can cause a physician unfamiliar with the supplement use to misinterpret routine lab results. If you take creatine and have a creatinine-based GFR (kidney function) test, inform your physician so the result is interpreted correctly. A better kidney function marker to track on creatine is cystatin C, which is not affected by creatine supplementation.

Honesty Scale: Solid (1) for creatine safety in healthy adults without kidney disease.

What to do: 3–5 g/day creatine monohydrate in water, any time of day. No loading phase required (though 5 days of 20–25 g/day loading does speed muscle saturation, both approaches work). Inform your physician you take creatine so routine kidney function labs are interpreted accurately.

For the full picture, read The Supplementation Deep Dive