Creatine is a small molecule synthesized from three amino acids — arginine, glycine, and methionine — and stored mostly in skeletal muscle as phosphocreatine. Your body makes about a gram of it a day. You get another gram or two from meat and fish. Most people walk around mildly under-saturated, which is the gap a $15 jar of monohydrate powder fills. The result is one of the few supplements where the trials are so numerous, the safety profile so well-mapped, and the cost so trivial that the honest question is not “should I take it” but “why aren’t you already.”
What the trials actually show
The single best summary is the International Society of Sports Nutrition position stand, which reviews several hundred trials and concludes that creatine monohydrate is the most effective ergogenic supplement currently available for high-intensity training and lean mass.1 A typical 4–12 week protocol of 3–5 g per day, combined with resistance training, produces roughly 1–2 kg of additional lean tissue and meaningful gains on bench press and squat compared with placebo.
The benefits extend well past the gym. A 2017 meta-analysis of older adults — the population most at risk for sarcopenia — found that creatine plus resistance training added about 1.4 kg of lean mass and improved upper-body strength versus training alone.2 In a population whose primary mortality risk after 65 is functional decline, that is not a cosmetic outcome.
The cognitive literature is smaller but pointed. A systematic review of randomized trials found that creatine supplementation reliably improved short-term memory and reasoning in conditions of metabolic stress — vegetarians, sleep-deprived adults, the elderly — even when it did not move the needle in young, well-fed omnivores.3 An earlier crossover trial of 5 g per day for six weeks in vegetarians showed measurable improvements on the Raven’s Progressive Matrices and a backward digit-span task.4
How the molecule actually works
Skeletal muscle runs on ATP, but it stores only a few seconds’ worth at any time. The phosphocreatine system is the body’s first-line ATP buffer: a phosphate group hops from creatine phosphate to ADP to regenerate ATP almost instantaneously, which is why creatine matters most in the 1–10 second window of a heavy lift or a sprint. Supplementation raises intramuscular creatine stores by roughly 20–40 percent in most people. The same energetic logic applies in the brain, where neuronal metabolic demand spikes during cognitively taxing work — and where Gualano and colleagues have argued creatine plays a measurable role in the aging brain.5
How to use it
The boring protocol is the right one: 3–5 grams of creatine monohydrate per day, every day, with or without food. There is no need for a loading phase unless you want saturation in a week instead of three. There is no compelling evidence that creatine HCl, ethyl ester, buffered creatine, or other proprietary forms outperform plain monohydrate — they are simply more expensive ways to deliver the same molecule. Buy unflavored micronized monohydrate; mix it into water, coffee, or a smoothie.
Two practical notes. The first 2–4 weeks usually bring a 1–2 kg gain in body weight that is intracellular water in muscle, not fat. This is a feature, not a bug. The second: serum creatinine, a kidney function marker, will read higher on creatine because the test measures creatinine and creatine spills into the pool — this is a laboratory artifact, not kidney damage, and any clinician should know to interpret it accordingly.
What it is not
Creatine is not a steroid. The lean-mass gains are real but modest, and they require training; without resistance work, there is nothing for the extra ATP to drive. It is not a stimulant, so taking it pre-workout does not “feel” like anything in the acute sense. The much-recycled claim that creatine causes hair loss traces back to a single 2009 trial in rugby players showing an increase in DHT — a single small study that has not replicated and that did not measure hair loss directly.
The honest summary is that creatine is the rare supplement where the cost-benefit ratio is so lopsided that it survives even an aggressive skeptic’s filter: pennies a day, decades of human data, gains that compound across the years you spend lifting and the decades after you stop.