Creatine

What it is, which is less exotic than the packaging suggests

Creatine is a compound your liver already makes and your muscles already store, and you eat about a gram a day of it in meat and fish. Supplementing raises muscle stores by something like twenty to forty per cent above what food alone provides.

What those stores do is regenerate ATP during very short, very hard efforts. The first few seconds of a sprint or a heavy set run on a phosphate system that empties fast and refills from creatine. More stored creatine means the refill is quicker, which means one more repetition, which — repeated over months — means more work done and more adaptation.

That is the whole mechanism. It does not build muscle directly; it lets you train slightly harder, and the training builds the muscle.

Where the kidney warning came from

Creatine raises blood creatinine, which is the marker laboratories use to estimate kidney function. So a routine blood test in someone taking creatine can look like impaired kidneys while the kidneys are entirely fine — the marker moved, not the organ.

That artefact became a health warning and has stayed in circulation for twenty-five years. Controlled studies, including ones running for years, have not found kidney harm in healthy adults. The position stands are unusually direct about this.

The genuine caveat: if you have existing kidney disease, this is a conversation with a clinician rather than a decision to make from an article. And if you are having blood tests, mention that you take it, so nobody chases a number that has a boring explanation.

Loading, cycling, and other things you do not have to do

Loading works and is not necessary. A high dose for five to seven days fills the stores quickly; a maintenance dose fills them just as completely in about three to four weeks. The only reason to load is impatience, and the cost of loading is that it is the phase where stomach upset happens.

Cycling off has no evidence behind it at all. The stores simply decline back to baseline over about a month, which is not a benefit.

The form is settled too: creatine monohydrate. The more expensive variants have not outperformed it in head-to-head trials, and monohydrate is the one all the research was done on.

The weight gain, which is real and is not fat

Creatine draws water into muscle cells. The scale goes up by a kilogram or two in the first weeks and that is intracellular water, not fat and not bloating in the usual sense of the word.

For most people this is irrelevant or mildly positive. For anyone in a weight-class sport or an endurance event where every kilogram is carried up a hill, it is a real trade-off to think about rather than dismiss.

What we are not claiming

There is a growing literature on creatine and cognition, particularly under sleep deprivation, and some of it looks interesting. It is much younger and much smaller than the muscle literature, and it is not the reason to take it.

This page is confident about the strength and lean mass findings because thirty years of trials agree. It is deliberately not confident about the rest, and the table says which is which.