Creatine, explained: what it does, who it's for, and what it doesn't do

Creatine, explained: what it does, who it’s for, and what it doesn’t do

Creatine has an unusual status in the supplement world: it’s one of the very few products backed by genuinely strong, decades-deep research, rather than marketing that’s outrun the evidence. But it’s also increasingly sold as a general-purpose brain enhancer, a claim the science supports far less confidently. Here’s what creatine actually does, and where the evidence quietly runs out.

What creatine actually does

Creatine is a naturally occurring compound made in the liver and kidneys, and obtained from food (mainly red meat and seafood), with roughly 95% stored in skeletal muscle. Supplementing with it increases the muscle’s stored phosphocreatine, which the body uses to rapidly regenerate ATP, the immediate energy currency for short, high-intensity efforts like lifting weights or sprinting. More stored fuel for that specific energy system translates into being able to do slightly more work per set, which compounds into meaningfully better training adaptations over weeks and months.

This is backed by an unusually large body of evidence. The International Society of Sports Nutrition’s position stand, a formal review of the accumulated research, states plainly that creatine monohydrate is the most effective nutritional ergogenic aid currently available to athletes for increasing high-intensity exercise capacity and lean body mass during training, a conclusion echoed by other major sports nutrition and dietetics bodies. Few supplements have anywhere near this level of consistent, replicated support.

Is it actually safe?

This is the question that generates the most anxiety, largely because creatine supplementation raises serum creatinine, a marker doctors also use to assess kidney function, which understandably worries people. But research specifically designed to test this has found the concern doesn’t hold up in healthy individuals: a recent systematic review and meta-analysis of creatine’s effects on kidney function found no adverse impact on renal markers in healthy people using standard doses, and broader safety reviews addressing cancer risk, dehydration and gastrointestinal effects have similarly found the available evidence doesn’t support these commonly circulated concerns.

The caveats worth knowing: research specifically in people with pre-existing kidney conditions and in pregnant women remains limited, so the “no evidence of harm” conclusion is best understood as applying to healthy adults, not universally. If you have an existing kidney condition, that’s a genuine reason to check with a doctor before starting, not because of strong evidence of harm, but because the safety research simply hasn’t been done in that population.

The cognition claims: where evidence gets thinner

Creatine’s marketing has expanded well beyond the gym in recent years, into claims about memory, focus and general brain health. The underlying biological logic is real: creatine does support brain energy metabolism, and supplementation has been shown to increase brain creatine concentration, albeit modestly. But a systematic review examining the cognitive claims specifically found the research provides only limited support for creatine as a general cognitive enhancer, describing the evidence as “somewhat equivocal.”

A more recent 2024 meta-analysis of 16 randomised controlled trials found small improvements in memory, attention and information-processing speed, but no statistically significant improvement in overall cognition or executive function. The authors themselves flagged the need for larger, more robust trials before drawing firm conclusions. That’s a genuinely different evidence tier from the exercise-performance research: promising and biologically plausible, but not yet the settled, heavily replicated finding that creatine’s strength and muscle-mass benefits represent.

Where the cognitive evidence is stronger: stressed states

The clearest exception to that thinner evidence base is in conditions that place unusual demands on brain energy metabolism, particularly sleep deprivation. Several controlled studies have found a single high dose of creatine measurably reduced sleep-deprivation-induced decline in cognitive tasks including processing speed and vigilance, alongside detectable changes in brain energy metabolites during the deprivation period. The proposed mechanism is straightforward: a fatigued, energy-depleted brain draws more heavily on the same ATP-regeneration system creatine supports in muscle, so supplementation has more room to make a measurable difference than it does in a well-rested brain that isn’t running short on energy.

Research in older adults shows a broadly similar pattern: more consistent benefit, particularly for memory, than in young, healthy, well-rested adults, plausibly for the same reason: ageing is associated with somewhat reduced brain energy efficiency, creating more “room” for supplementation to help.

Who creatine is actually a good fit for

People doing regular resistance or high-intensity training have by far the strongest evidence base to draw on. This is where creatine’s research is deepest and most consistent.

Older adults, particularly when combined with resistance training, have reasonably good evidence for benefits to both muscle mass and, more tentatively, cognitive measures like memory.

People who are sleep-deprived or under unusual cognitive load may see a real, if modest, benefit based on the stressed-state research, though this isn’t the same as a daily nootropic claim for well-rested people.

Healthy adults hoping for a general brain boost have the weakest evidence to point to. It’s a reasonable thing to try, but it’s not backed by the kind of settled science that applies to creatine’s exercise benefits.

The honest takeaway

Creatine’s reputation as one of the best-evidenced supplements available is earned: for exercise performance and lean mass, the research is deep, consistent and unusually strong for the supplement category. The kidney-safety fears in healthy people aren’t well supported. But the newer wave of cognitive-enhancement marketing has outpaced the science: there’s a real, biologically plausible signal, strongest in stressed states like sleep deprivation, but it’s not yet the settled case that exists for creatine and muscle.

Keep reading: Creatine does its work alongside training and enough protein, so see strength training for beginners and protein: how much do you actually need. For a closer look at women specifically, there’s creatine for women.

FAQs

Does creatine damage your kidneys?

Research specifically testing this in healthy individuals, including recent systematic reviews, has found no adverse effect on kidney function at standard doses. Evidence is more limited for people with existing kidney conditions, who should check with a doctor first.

Is creatine only useful for bodybuilders?

No. The evidence base covers general resistance training, high-intensity intermittent exercise, and even some clinical and ageing-related applications, not just bodybuilding specifically.

Does creatine actually improve brain function?

The evidence is mixed and considerably weaker than for exercise performance. The clearest cognitive benefits appear in specific stressed states, sleep deprivation and older age, rather than as a general enhancer for well-rested, healthy adults.

How much creatine should I take?

This article covers what the research shows about effects, not personalised dosing advice. Standard protocols in the research typically use a maintenance dose in the low single-digit grams per day range, but check product guidance or a healthcare professional for your specific situation.

Do women respond to creatine differently than men?

Some research suggests women may see somewhat smaller strength and muscle-mass gains from creatine during training compared with men, though the reasons aren’t fully established and sex-specific safety research remains more limited than general population data.

Is creatine safe for long-term daily use?

The available safety literature, spanning studies since the late 1990s, generally supports long-term use in healthy individuals at standard doses without evidence of significant harm, though most trials run for weeks to a few years rather than decades.