A summary of published research, not medical advice. See the Disclaimer.
Studies: every indexed trial and review on this topic, scored
Creatine is a compound made from amino acids. Muscle stores most of it as phosphocreatine, which helps regenerate ATP during short, hard efforts. The body makes some, and meat and fish supply more. Most trials used creatine monohydrate.
Best-supported effect: Strength gains during resistance training in adults under 50. Helps (strong evidence).
Most-cited weak claim: Better memory and thinking. May help a little (weak evidence).
How we grade evidence · Last reviewed: October 2026
What you need to know
In adults under 50 doing resistance training, a 2024 pooled analysis of 23 trials found that creatine added to training raised strength more than placebo. That finding has strong evidence behind it. Muscle size grew a little more than with training alone, with moderate evidence. Results for older adults, memory, thinking and depression rest on fewer or smaller trials, so the evidence is weak. In healthy people, pooled trials found no change in kidney filtration, though blood creatinine rose a little, and a few case reports describe kidney injury. Most people in the strength trials were men; safety in children and adolescents has not been established, and a review flags a possible higher kidney risk in people with past kidney disease or on medicines that can harm the kidneys. Reviews report usual study doses of 3 to 5 g a day, and cognition trials used about 2 to 20 g a day.
| Effect | Verdict | What was measured | Studied in |
|---|---|---|---|
| Muscle strength | Helps (strong evidence) Pooled analysis of 23 trials in adults under 50, strength gains over placebo |
Measured | Adults under 50, mostly men, with resistance training |
| Muscle size | Probably helps a little (moderate evidence) 10 pooled trials, small effect, results could not rule out no effect |
Measured | Healthy adults, with resistance training |
Muscle strength: A 2024 meta-analysis of 23 trials in adults under 50 found that creatine plus resistance training increased upper- and lower-body strength more than training plus placebo [1]. Most participants were men; women in the few female trials showed no significant gains. Helps (strong evidence): many trials measured strength directly and the pooled result was clear.
Muscle size: A 2023 meta-analysis pooled 10 trials that measured regional muscle size directly with ultrasound, MRI or CT. It found a small increase with creatine plus resistance training over training alone [3]. Probably helps a little (moderate evidence): downgraded because the effect was small and its uncertainty range included no effect.
| Effect | Verdict | What was measured | Studied in |
|---|---|---|---|
| Hair loss | May make little or no difference (weak evidence) One small 12-week trial in young trained men only |
Measured | Resistance-trained men aged 18 to 40, one 12-week trial |
Hair loss: A 2021 expert review lists hair loss among the common concerns raised about creatine, mainly through a possible rise in DHT [8]. In a 12-week randomized trial, 45 resistance-trained men aged 18 to 40 received 5 g/day of creatine or a maltodextrin placebo; 38 completed it. DHT, the DHT-to-testosterone ratio, hair density, follicle count and hair thickness did not differ between groups [22]. May make little or no difference (weak evidence): one small trial with fewer than 500 people, in young trained men only.
| Claim | Verdict | What was measured | Studied in |
|---|---|---|---|
| Strength and lean mass | May help (weak evidence) Few trials, 357 older adults, several strength measures showed no difference |
Measured | Older adults (average age about 64), with resistance training |
| Memory | May help a little (weak evidence) Only 8 trials pooled in healthy people, results varied widely |
Measured | Healthy people aged 11 to 76 |
| Other thinking skills (attention, reaction time, reasoning) | Unclear: trials disagree (weak evidence) Small trials with inconsistent results across thinking skills |
Measured | Healthy people |
| Depression symptoms | Unknown (very weak evidence) Early trials of unstated size plus lab and theory work, no adequately sized trial |
Self-reported | People with depression (early trials) |
Strength and lean mass in older adults: A 2014 meta-analysis of randomized trials in older adults found greater gains in fat-free mass and in chest-press and leg-press strength when creatine was added to resistance training [2]. May help (weak evidence): few trials with 357 people in total, and several other strength measures showed no difference.
Memory: A 2023 meta-analysis of RCTs in healthy people found a small improvement in memory scores, larger in older adults than in younger ones [4]. May help a little (weak evidence): only 8 trials were pooled and their results varied widely.
Other thinking skills: A 2018 systematic review of six RCTs found possible gains in short-term memory and reasoning, with inconsistent results for other domains [5]. A 2024 systematic review found that creatine raises brain creatine content to a limited extent and has equivocal effects on cognition [6]. Unclear: trials disagree (weak evidence); the trials were small.
Depression: A 2019 review describes evidence that disrupted brain energy use is involved in depression and reports that early clinical trials suggest creatine may work as an antidepressant [7]. Unknown (very weak evidence): the review does not give the size or design of the early trials, and no adequately sized trial has tested depression.
No adequately sized trials have tested long-term effects on cognition or effects on depression.
Researchers have several ideas about how creatine could affect muscle or the brain. Some steps have been measured in people, some only in animals or lab cells. Each theory below explains the idea step by step, then lists what supports it and what is missing or unclear.
Muscles run on ATP, a molecule that releases energy when it gives up one of its phosphates [28]. During hard exercise, muscle can use ATP up to 1,000 times faster than at rest, so ATP has to be rebuilt as fast as it is used [28]. The quickest way to rebuild it is phosphocreatine (creatine with a phosphate attached). An enzyme called creatine kinase moves the phosphate from phosphocreatine back onto the used ATP almost instantly [28]. In a sprint or heavy set, phosphocreatine can run low within about 10 seconds [28]. After that, ATP has to come more from breaking down sugar (glucose and glycogen), which is slower to reach full speed, and the effort fades [28]. After hard exercise, refilling phosphocreatine takes from under 5 minutes to more than 15 minutes [28].
Taking creatine raises the muscle's creatine, and part of it is turned into phosphocreatine [12]. The theory is that a bigger phosphocreatine store lets muscle keep rebuilding ATP at a high rate for a little longer during an effort, and refill faster between sets. Creatine does not add ATP itself; it adds to the phosphocreatine that rebuilds ATP [28].
Evidence for
Evidence against or unclear
This builds on Theory 1. If phosphocreatine lasts a little longer in each set, a person may manage a few more repetitions or a slightly heavier weight. Over weeks of training, that adds up to more total weight lifted. The theory is that this extra work, repeated over weeks, adds muscle, and that creatine's effect on muscle size comes mostly from better training sessions, not from creatine building muscle directly [24].
Evidence for
Evidence against or unclear
Creatine is moved into muscle cells and builds up there. Water follows it in, so the cells swell slightly [16]. Muscle cells can sense their own volume, and early research proposed that this swelling acts as a stress signal that switches on the pathways that build muscle protein [16]. The theory is that creatine raises muscle protein building partly through this swelling.
Evidence for
Evidence against or unclear
Each muscle fibre is one long cell with many nuclei. Extra nuclei come from satellite cells, stem cells that sit next to the fibre, increase in number with strength training, and can join the fibre [26]. More nuclei are thought to let a fibre grow larger [26]. The theory is that creatine increases the number of satellite cells and the nuclei they add, so fibres can grow more with training [16][26].
Evidence for
Evidence against or unclear
Brain cells also use creatine kinase and phosphocreatine to rebuild ATP quickly when energy demand jumps [17]. The theory is that raising brain creatine raises this phosphocreatine reserve, which could help the brain keep up ATP when it is under strain, such as during sleep loss, low oxygen or hard mental tasks [27].
Evidence for
Evidence against or unclear
Brain imaging, genetic and animal studies suggest that in depression the brain may make, store and use energy (ATP and phosphocreatine) less well [7]. The theory is that extra creatine raises the brain's phosphocreatine reserve and helps correct this energy problem in some people [7].
Evidence for
Evidence against or unclear
Cells constantly produce reactive oxygen molecules, such as the hydroxyl radical, which can damage them. One idea is that creatine reacts with these molecules directly and neutralizes them [14]. A second is that in mitochondria, where most ATP is made, creatine kinase helps limit how many of these molecules form [17]. A third is that phosphocreatine binds to cell membranes and helps keep them stable [17].
Evidence for
Evidence against or unclear
Overall: Creatine raising muscle creatine and phosphocreatine is shown in people [11][12][23]. How that leads to more strength and muscle is still being worked out [16], and the brain theories rest on weaker evidence [6].
| Side effect | Verdict | How often vs placebo | Source | Studied in |
|---|---|---|---|---|
| Body weight gain (older adults) | Probably happens (moderate evidence) One pooled analysis of older adults, total mass up, fat mass unchanged |
Not reported | [2] | Older adults |
| Small rise in blood creatinine | Probably happens (moderate evidence) Pooled analysis found slight, brief rise linked to creatine turnover in the body |
Not reported | [9] | |
| Reduced kidney function (healthy people) | Probably no harm (moderate evidence) Pooled data from about 440 people, no clear change in kidney filtration |
Not reported | [9] | Healthy people |
| Acute kidney injury | Unknown (very weak evidence) Only a few reports of single patients with kidney injury |
Case reports only | [18][19] | Patients with kidney injury |
| Cramping | May not increase it (weak evidence) Reviews only, well tolerated in healthy people, cramping rates not reported |
Not reported | [8][10] | Healthy people |
| Dehydration | May not increase it (weak evidence) Reviews only, well tolerated in healthy people, dehydration rates not reported |
Not reported | [8][10] | Healthy people |
| Hair loss | May not increase it (weak evidence) 38 trained men finished 12 weeks, no hair differences from placebo |
No difference at 12 weeks (38 men) | [22] | 38 trained men |
In older adults, total body mass rose more with creatine plus training than with training alone, with no change in fat mass [2]; an expert review discusses whether early weight gain is water held in muscle [8]. The creatinine rise can be mistaken for reduced kidney function; the kidney meta-analysis found no significant change in filtration rate (about 440 participants pooled) [9]. Reviews describe creatine as well tolerated in healthy people at doses up to 30 g/day for 5 years [10].
This lists what studies and labels report. A pharmacist or prescriber can say whether it applies to a specific person.
This lists what studies and labels report. A pharmacist or prescriber can say whether it applies to a specific person.
| Combined with | What happened | Verdict | Source | Studied in |
|---|---|---|---|---|
| Caffeine, daily during creatine use | 2 of 6 studies found caffeine blunted creatine's performance benefit; 3 found no interaction and 1 found added benefit. Gut discomfort is one proposed reason | Unclear: studies disagree (weak evidence) Mixed results across 6 studies, 2 found a weakened benefit, 3 no interaction |
[20] | |
| Caffeine, single dose before exercise after creatine loading | 3 of 4 studies found creatine loading did not interfere with caffeine's effect | Probably no harm (moderate evidence) 3 of 4 studies found no interference with caffeine's effect |
[20] | |
| Caffeine or carbohydrate (uptake) | A pharmacokinetic review states both may affect creatine uptake through its transporter; data are very limited | Unknown (very weak evidence) Review of drug-level studies only, with very limited data |
[21] | |
| Medicines that can damage the kidneys | A review reports a possible higher risk of kidney dysfunction | Unknown (very weak evidence) Single review reports possible risk, no controlled drug trials found |
[18] | |
| Several other bodybuilding supplements | One case of acute interstitial nephritis, resolved after stopping all supplements | Unknown (very weak evidence) Report of a single patient taking several supplements at once |
[19] |
No controlled trials of creatine with prescription drugs were found in these sources.
These are the amounts used in the studies. They are not recommendations.
Reviews report study doses of 3 to 5 g a day, or about 0.1 g/kg of body weight per day [8]. Some regimens start with a higher-dose loading phase, and an expert review discusses whether loading is needed [8]. Resistance-training trials generally ran from about 6 weeks to several months [2][3]. Cognition trials used doses of about 2–20 g/day and lasted from 5 days to 24 weeks [4].