Creatine: what it does, who it's for, and what the evidence shows

What creatine is and how it works

Creatine is a small compound the body makes in the liver, kidneys and pancreas from three amino acids: arginine, glycine and methionine. About 95% of it ends up in skeletal muscle, mostly as phosphocreatine, with smaller amounts in the brain and other tissues.

Phosphocreatine works as a quick-access phosphate reserve. During a heavy lift or a sprint, it donates a phosphate group so muscle cells can regenerate ATP, their energy currency, faster than they otherwise could. The 2017 International Society of Sports Nutrition position stand [28615996] describes how muscle stores and uses creatine this way, and supplementation raises that stored pool.

That mechanism is well established. What it adds up to for a particular person, at a particular dose, over a particular training program is a separate question, and most of this article is about that gap. Nearly every supplement sold as creatine is creatine monohydrate, the form most clinical trials have tested. Our creatine topic hub collects deeper pieces on individual questions.

Where it comes from, and why your starting point matters

Dietary creatine comes almost entirely from animal muscle, so meat and fish are the sources that count. Plant foods contain essentially none. A typical omnivore takes in roughly 1 to 2 g a day from food, on top of what the body makes, which is below the 3 to 5 g a day most maintenance research has used.

Vegetarians and vegans generally start with lower muscle creatine stores than meat and fish eaters, and women average lower baseline stores than men [39796530, 16573356]. That describes where the starting number tends to sit. The research has not established a separate dose for either group.

It also helps to separate creatine from creatinine. Creatinine is the waste product of creatine breakdown, and it is what routine blood tests use to estimate kidney function. Because supplements enlarge the pool creatinine comes from, the number can rise slightly without any change in the kidneys. Tell your clinician you take creatine before a kidney panel so the result is read in context.

What the evidence supports: strength, power and lean mass

This is where creatine's record is strongest. A 2025 meta-analysis of 69 studies found creatine plus resistance training improved bench press, squat strength and jump and sprint power, with no significant effect on handgrip or leg press strength [40944139]. The gains were clearest in younger adults and males.

Lean mass follows a similar pattern. A 2022 meta-analysis of 35 studies found creatine raised lean body mass only when paired with resistance training, not with other exercise or none, and the increase was significant in men but not in women [35986981]. Creatine on its own, without training, is not a muscle-building shortcut.

Older adults appear to benefit when they train. A meta-analysis of 22 studies in people with an average age of 57 to 70 found creatine plus resistance training increased lean tissue and both chest and leg press strength more than training alone [29138605]. In older women specifically, a 10-study meta-analysis found upper-body strength improved, but lower-body strength and muscle mass changed only when programs ran at least 24 weeks [34836013]. In postmenopausal women, a 2026 meta-analysis of 7 trials found small gains in lean mass and leg strength, mainly at 5 g a day or more [42141930].

Early weight gain on creatine is largely water. A one-week trial found total body water rose about 2%, which reflects fluid in the muscle and not new tissue [37675500]. Effects on body fat are small and inconsistent: meta-analyses report slight differences in body fat percentage, but absolute fat mass changes were not statistically significant in either adults under 50 or those 50 and older [37892421, 33467377].

Brain, mood and other claims: where the evidence thins out

Creatine's reputation has outgrown its trial base in several areas. Some findings are encouraging, some are small or uncontrolled, and a few are negative. Here is a quick map.

Two cautions deserve mention. In a trial of 35 people with bipolar depression, creatine did not beat placebo on the main depression scale, and two people taking it had a manic or hypomanic switch [29177955]. And in cancer, mouse studies conflict: older work suggested creatine slowed tumor growth, while newer models linked it to more spread of certain cancers [34895811, 42449108]. That is animal data, not a human finding, but it is a reason to talk with an oncology team before supplementing.

Rare inherited creatine deficiency disorders are a different matter. They are diagnosed genetically and treated with prescription-level dosing under a metabolic specialist, and they say nothing about ordinary supplement use [20301745, 19289269].

How much, what kind and when

Most research uses 3 to 5 g a day as a maintenance dose, and one scoop of plain monohydrate typically provides 5 g. Some trials begin with a loading phase of about 20 to 25 g a day for five to seven days, which fills muscle stores faster. It is not the only route. In a 6-week trial, about 2.3 g a day with no loading raised plasma creatine and improved fatigue resistance [20591625], so a steady daily dose gets there more slowly.

If you load, split the dose. In a 28-day trial in soccer players, one 10 g dose caused diarrhea about twice as often as the same total taken as two 5 g doses, or as placebo [18373286].

On timing, the data are underwhelming in a useful way. An 8-week trial in 34 resistance-trained athletes found no difference between taking creatine before or after a workout [36465581], and a 2021 review judged the evidence too weak to call either one better [34445003]. Our piece on the best time to take creatine covers the comparisons in more detail. Taking it daily is what the research supports.

Food can change uptake. In a trial of 24 men, adding a large carbohydrate dose (93 g) increased muscle creatine retention by 60% versus creatine alone [8944667]. That was a specific, large dose and the study did not test strength or performance outcomes, so it does not mean you need a carbohydrate chaser.

On form, monohydrate remains the benchmark. A buffered product performed no better than monohydrate on muscle creatine, body composition, strength or power over 28 days [22971354]. Creatine ethyl ester was less effective at raising serum creatine and raised creatinine more [19228401]. Creatine hydrochloride is about 38 times more soluble in water, but that is a lab solubility finding and not a human performance result [22432515]. Mixing is not a stability problem either: creatine dissolved in water loses meaningful content over weeks, not the minutes it takes to drink it [12916907].

Safety, side effects and who should be careful

For healthy adults, the safety record is reassuring. The ISSN position stand concluded supplementation is safe and well tolerated across the doses and durations it reviewed [28615996]. A review of 19 studies covering 5 to 30 g a day for anywhere from 5 days to 5 years found no known harmful effect on kidney function in healthy people [30367015]. A 2025 analysis of 685 creatine trials found no overall increase in side effects versus placebo [40198156].

Some common worries have not held up. A randomized crossover trial found a week of high-dose creatine did not worsen hydration, temperature regulation or heat-illness symptoms during exercise in the heat [16619091]. In the 2025 analysis, a small study-level difference in cramping disappeared once weighted by trial size [40198156]. Gastrointestinal upset is more likely with large single doses, and in one small trial it appeared only in a subgroup combining creatine with caffeine [26439785].

Hair loss gets attention online. It traces mainly to one trial of 20 male rugby players in which creatine loading raised blood DHT, a hormone linked to hair loss in susceptible people [19741313]. The trial never measured hair, and no larger trial has followed it up. It is a thin signal on a hormone marker, not evidence of hair loss.

Who it's for, and a sensible way to start

The best-supported use is for people who do resistance or high-intensity training and want modest gains in strength, power or lean mass. Vegetarians and vegans, who start with lower stores, and older adults who are strength training are also reasonable candidates. Without training, the lean-mass evidence largely disappears.

• Choose plain creatine monohydrate; newer forms have not shown an edge.
• Take 3 to 5 g a day, every day, at whatever time you will remember.
• Skip loading unless you want faster saturation, and split it if you do.
• Expect water-weight gain in the first week, not fat or muscle.
• Judge results over weeks of consistent training, not days.

Creatine is not a treatment for any condition, and the headline claims about mood, memory, blood sugar and aging outrun the controlled evidence. It is best understood as a modest, well-studied training aid with a good safety record in healthy adults.