Creatine
The most well-studied ergogenic supplement there is — for strength, lean mass, and increasingly for older adults' brains too.
Not medical advice — talk to a doctor before starting, especially if you have kidney disease or take medication that affects kidney function.
How It Works
Creatine is stored in muscle as phosphocreatine, a rapid-reserve fuel your cells use to regenerate ATP during short, high-intensity effort — a heavy set, a sprint, a jump. Supplementing raises muscle creatine stores above what a typical diet (mostly from meat and fish) provides, which lets you produce slightly more force over repeated short efforts and recover a little faster between sets. That small per-set edge, compounded over months of training, is what drives its strength and lean-mass effects — it isn't a direct muscle-builder on its own.
The Research
Creatine monohydrate is widely regarded as the most extensively researched and consistently effective legal ergogenic supplement available — the evidence for strength and lean-mass gains is strong, not preliminary.
Position stand: Kreider RB, et al. "International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine," Journal of the International Society of Sports Nutrition, 2017. Concludes creatine monohydrate is the most effective nutritional supplement currently available for increasing high-intensity exercise capacity and lean body mass during training, with doses up to 30g/day used safely for up to 5 years in published research.Read the position stand →
Women and older adults: the research base — and the marketing around creatine — has shifted noticeably in recent years toward audiences beyond young male lifters.
Forbes SC, Candow DG, Ostojic SM, Roberts MD, Chilibeck PD. "Meta-Analysis Examining the Importance of Creatine Ingestion Strategies on Lean Tissue Mass and Strength in Older Adults," Nutrients, 2021. Pooling 20 RCTs in adults averaging over 50, creatine combined with resistance training produced meaningfully greater lean tissue mass (roughly 1.3kg more) and greater strength gains than resistance training with a placebo.
Read the meta-analysis →
Smith-Ryan AE, Cabre HE, Eckerson JM, Candow DG. "Creatine Supplementation in Women's Health: A Lifespan Perspective," Nutrients, 2021. Notes that women typically carry 70–80% lower resting creatine stores than men, and reviews evidence that supplementation can support strength and exercise performance in women across life stages — including during pregnancy, postpartum, and menopause, where interest has grown the most.
Read the review →
Cognitive effects are a genuinely separate, newer line of research from the strength/lean-mass evidence above — early trials suggest a possible benefit for tasks affected by sleep deprivation or mental fatigue, particularly in older adults, but this body of work is smaller and less mature than the decades of strength research, so it's fair to call it promising rather than settled.
Loading Phase vs. Steady Dosing
Two approaches show up in the research, and both work — they just get you to the same place at different
speeds:
Loading: ~20g/day (split into 4 doses) for 5–7 days, then a maintenance dose. This
saturates muscle creatine stores faster, typically within about a week.
Steady dosing: 3–5g/day from the start, no loading phase. This reaches the same
saturated muscle stores as loading — it just takes roughly 3–4 weeks to get there instead of one.
The ISSN's own guidance on common misconceptions confirms loading isn't required for creatine to
"work" — it only changes how quickly you reach full saturation. Most people who don't need faster results
(i.e., aren't a week out from a specific event) do fine simply starting at 3–5g/day.
Read the ISSN's guidance on creatine misconceptions →
Typical Dosing
Maintenance: 3–5g/day of creatine monohydrate, taken any time of day, with or without food — timing relative to training doesn't appear to matter much. Loading (optional): ~20g/day split into 4 doses for 5–7 days, then drop to maintenance. Source: ISSN position stand, above.
Who Should Be Cautious
Per the ISSN position stand, there's no evidence of kidney damage from creatine at recommended doses in healthy people, even in studies running several years — but anyone with existing kidney disease, or on medication that affects kidney function, should check with a doctor before using it. The most common side effects are mild GI discomfort and water retention, both more noticeable during a loading phase than at a steady 3–5g/day.