Does creatine work, and is it safe?

Creatine is among the most researched supplements in existence, and the evidence for both effectiveness and safety in healthy adults is unusually strong — which distinguishes it from almost everything else sold in the category.

What it does. Creatine is stored in muscle as phosphocreatine, which rapidly regenerates ATP during short, intense effort. Supplementation increases muscle stores by roughly 20–40%, extending how long the phosphagen system can sustain maximal output.

The practical effect: a few extra repetitions at a given load, or slightly more power in repeated sprints. Over months, that additional training volume produces measurably greater strength and lean mass gains than training alone. Creatine does not build muscle directly — it lets you train slightly harder, and the training builds the muscle.

Typical findings are modest but consistent: improvements in strength and power of a few percent, and greater lean mass gains over a training programme.

What form and dose. Creatine monohydrate is the form with the overwhelming majority of the evidence, and it is the cheapest. The various "advanced" forms sold at higher prices have not demonstrated superiority. A common protocol is 3–5g daily; a loading phase of around 20g daily for a week saturates stores faster but is not necessary.

Safety. Decades of studies, including multi-year trials, have found no harmful effects on kidney or liver function in healthy individuals. The kidney concern originated from the fact that creatine raises creatinine, a marker used in kidney function tests — the marker rises without kidney damage, which caused misinterpretation. Anyone with existing kidney disease should take medical advice.

Weight gain is real but is water. Creatine draws water into muscle cells, commonly adding 1–2kg. This is intracellular, not bloating.

Non-responders exist — people with already-high muscle stores see little effect.

Research into cognitive effects is ongoing and less settled.