Creatine: What It Does, Potential Benefits, and What to Know

Creatine is best known as a sports supplement, but it is also a compound the body makes and uses every day. Research most strongly supports its use for improving strength and repeated high-intensity exercise, especially when combined with resistance training. Other potential benefits—including effects on cognition and the sleep-deprived brain—are promising areas of research, but they remain less certain.

What is creatine?

Creatine is a nitrogen-containing compound made in the body from the amino acids arginine and glycine, with methionine contributing a methyl group during the final step of synthesis. We also get creatine from foods such as meat and fish, and from supplements. About 95% of the body’s creatine is stored in skeletal muscle; smaller amounts are found in tissues including the brain and heart. ^[1]

Creatine helps cells manage energy. Inside cells, it can take on a phosphate group to form phosphocreatine. When energy demand rises quickly, the enzyme creatine kinase transfers that phosphate to ADP, helping regenerate ATP—the cell’s immediately usable energy source. This creatine–phosphocreatine system acts as a rapid energy buffer, particularly in tissues with high or changing energy needs. ^[1]

Creatine is not the same as creatinine. Creatinine is a breakdown product of creatine and phosphocreatine that the body excretes in urine; it does not perform creatine’s energy-buffering role. ^[2]

Creatine and methyl groups

The body makes creatine in two main steps. First, enzymes use arginine and glycine to produce guanidinoacetate, or GAA. Then an enzyme called GAMT transfers a methyl group from S-adenosylmethionine (SAM) to GAA, producing creatine and S-adenosylhomocysteine (SAH). SAH can then be converted to homocysteine. ^[3]

This is why creatine synthesis is sometimes described as a “methyl sink”: making creatine inside the body uses methyl groups supplied by SAM. One widely cited estimate is that creatine synthesis accounts for about 40% of SAM-derived methyl-group use in young adults. That figure is an estimate, not a fixed amount for everyone; it depends on factors such as dietary creatine intake and the assumptions used in the calculation. ^[4]

Supplementing with creatine can reduce the body’s own production pathway, including lowering GAA. In theory, this may reduce the methyl-group demand of making creatine internally. But that biochemical effect should not be turned into a broad health promise: a randomized trial found that 3 g of creatine daily for 12 weeks lowered plasma GAA but did not significantly lower homocysteine or change measured blood SAM or SAH compared with placebo. ^[3]

Benefits: what research supports

Strength and high-intensity exercise are the best-established benefits. Creatine monohydrate increases muscle phosphocreatine and can help support repeated, brief, high-intensity efforts. Studies show benefits for strength, power, training capacity and lean mass—particularly when creatine is combined with resistance training. It is less consistently helpful for continuous endurance exercise. ^[1]

Older adults may gain a modest strength benefit when creatine is combined with resistance training. A 2026 meta-analysis of 11 randomized trials found a small improvement in muscle strength. The combined results did not show statistically significant gains in muscle mass or physical function, and the authors cautioned that the findings may not apply to frail or functionally limited older adults. ^[5]

Postmenopausal women may see modest gains in muscle when creatine is paired with resistance training. A 2026 meta-analysis of seven trials involving 608 women found a small average increase in lean mass and improvement in leg-press strength. Benefits were more apparent in studies that combined creatine with resistance training; the review did not find a meaningful overall improvement in bone mineral density. ^[6]

Cognitive benefits remain uncertain. A 2024 meta-analysis of 16 randomized trials reported a small improvement in memory and some timed attention and processing-speed measures. It did not find significant improvement in overall cognition or executive function, and certainty varied by outcome. A 2026 review focused on older adults found very little direct human evidence related to dementia, including no relevant randomized trials testing creatine as a treatment for dementia. In 2024, the European Food Safety Authority concluded that the evidence did not establish a cause-and-effect relationship between creatine supplementation and improved cognitive function. ^[7]

It is reasonable to describe cognition as an active research area, but not to promise that creatine improves memory, prevents dementia or treats neurological disease.

Could creatine help a sleep-deprived brain?

A small but intriguing body of research suggests that a large single dose of creatine may partly blunt some cognitive effects of one night without sleep. In a 2024 randomized, placebo-controlled crossover study, 15 healthy adults stayed awake for about 21 hours. After a single high dose of creatine monohydrate—0.35 grams per kilogram of body weight—participants performed better than after placebo on several cognitive tests, including measures of memory, processing speed, language, logic and numerical ability. Brain scans also showed changes in energy-related chemical signals. ^[8]

A 2026 study tested a lower single dose, 0.2 grams per kilogram, in 29 healthy adults during a similar period of sleep deprivation. Researchers reported less decline on some tests of logic, numerical ability, language-related processing speed and alertness. They reported improvements of up to 12% on certain measures—not a general 12% improvement in brain function. ^[9]

These findings are promising, but they are preliminary. A 2026 systematic review found only five eligible studies and concluded that early results trend in a positive direction, while emphasizing that the research remains sparse and needs better trials. Studies differ in their doses, sleep-loss conditions and cognitive tests, so it is not yet clear how reliable or meaningful the effects are in everyday life. ^[10]

The studies tested unusually large, one-time doses under controlled conditions. They do not show that a regular 3–5 g daily supplement has the same immediate effect, that creatine helps with chronic insufficient sleep, or that it prevents the broader consequences of sleep loss. The study doses should not be taken as a recommendation for self-treatment.

Creatine is not a substitute for sleep, and it should not be used to make driving or other safety-critical activities seem safe when someone is tired. Sleep deprivation can impair reaction time and judgment; a person who is very sleepy may not be able to reliably keep themselves awake. ^[14]

Side effects and safety

The latest large structured analysis examined side-effect reporting across 684 randomized controlled trials. Reported effects were generally infrequent and mild, and the analysis found no consistent increase in side-effect risk compared with placebo across the categories studied. However, side effects were not reported consistently in every trial, so the findings cannot guarantee that no individual will experience a problem. ^[11]

Potential issues to keep in mind include:

• Weight gain: Creatine can increase body weight, partly because muscles store more water. This is not the same as gaining body fat, but it may matter to people monitoring weight or competing in weight-class sports. ^[13]
• Stomach upset or diarrhea: Some people experience digestive symptoms, particularly after taking a large amount at once. Dividing a larger daily dose into smaller servings may help. ^[12]
• Kidney test interpretation: Creatine supplementation can raise blood creatinine because more creatine is being converted to creatinine. That can make creatinine-based estimates of kidney function harder to interpret; by itself, a higher creatinine result does not prove kidney damage. A 2025 meta-analysis found a modest increase in serum creatinine but no significant change in GFR. Anyone with kidney disease should discuss creatine and laboratory monitoring with a healthcare professional. ^[12]
• Pregnancy and breastfeeding: Evidence about safety in these situations is limited. Anyone who is pregnant or breastfeeding should consult a healthcare professional before using creatine.

Claims that creatine routinely causes dehydration or heat illness are not supported by the 2025 safety review, which found no evidence of impaired hydration or thermoregulation in controlled studies. As with any exercise, people should still drink appropriately, especially during activity in hot conditions. ^[12]

Use and product choice

Creatine monohydrate is the form with the largest research base. A common approach is 3–5 g daily without a loading phase; it takes several weeks to build up muscle stores. An optional loading approach uses 15–20 g daily, divided into servings of no more than 5 g, for 5–7 days, followed by a maintenance dose. ^[13]

For a supplement, choose a clearly labelled product that lists creatine monohydrate as the ingredient and gives the amount per serving. Independent quality certification can add reassurance about the product’s contents, though it does not prove that creatine is appropriate for every person.

The takeaway

Creatine is a naturally occurring energy-buffering compound—not a steroid and not simply a “muscle builder.” Its best-supported use is as an aid to resistance training and repeated high-intensity activity. Its role in the body’s own methyl-group use is real, but current human evidence does not show that supplementation reliably improves methylation or lowers homocysteine. Early sleep-deprivation studies are interesting, but they do not establish creatine as a way to compensate for lost sleep. ^[1][3][10]

Research checked through October 12, 2026. The 2026 safety analysis includes authors who report creatine-industry research, advisory or financial relationships. That does not invalidate the findings, but it is useful context when weighing supplement-safety claims. ^[11]

References

1. Creatine: mechanisms and clinical evidence (review).
2. Creatine and creatinine: clinical interpretation review.
3. Randomized trial of creatine supplementation, guanidinoacetate and methylation-related measures.
4. Creatine synthesis and methyl-group metabolism review.
5. 2026 meta-analysis of creatine and strength in older adults.
6. 2026 meta-analysis of creatine with resistance training in postmenopausal women.
7. 2024 systematic review and meta-analysis of creatine and cognitive performance.
8. 2024 controlled study of creatine during sleep deprivation.
9. 2026 study of creatine and cognitive performance during sleep deprivation.
10. 2026 systematic review of creatine and sleep deprivation.
11. 2026 structured analysis of side effects reported in randomized creatine trials.
12. 2025 review of creatine safety, kidney markers and hydration.
13. Health Canada: Creatine monohydrate.
14. CDC/NIOSH: Sleep deprivation and safety.