I'm generally skeptical of supplements. Most of the category is built on thin evidence, aggressive marketing, and the human preference for a purchasable solution over a behavioral one. Creatine monohydrate is one of the few exceptions, and it's worth understanding why.
What it actually does
Creatine helps regenerate ATP, the immediate energy currency your cells use for short, high-intensity work. Supplementing raises the amount stored in muscle, which allows slightly more work before fatigue. Over months, slightly more work per session compounds into meaningfully more strength and muscle.
That mechanism is straightforward, well characterized, and explains why the effect is consistent across a very large number of studies. This isn't a compound with an interesting hypothesis and thin data. It's among the most studied sports supplements in existence.
Why this matters for aging, not just athletes
The framing of creatine as a bodybuilding supplement has kept it away from the population that may benefit most. In older adults, creatine combined with resistance training has shown better gains in lean mass and strength than resistance training alone in multiple trials.
Given that muscle mass and strength are among the strongest predictors of functional independence in later life, a cheap, well-tolerated compound that improves the response to strength training is worth attention. There's also emerging work on bone density in older adults, though that literature is less mature and I'd call it promising rather than established.
The cognitive angle
Brain tissue also uses creatine, and there's a growing body of research on cognitive effects, particularly under conditions of stress: sleep deprivation, mental fatigue, and in vegetarians and vegans who have lower baseline stores from diet.
I'd characterize this honestly: the signal is real and interesting, the effect sizes in healthy, well-rested people appear modest, and the strongest findings are in populations under some form of deficit. If you're a well-slept omnivore, don't expect a noticeable cognitive change. If you're sleep-deprived or plant-based, the case is stronger.
Most supplements are a purchasable substitute for behavior. Creatine is one of the few that amplifies behavior you're already doing.
Practical use
Creatine monohydrate is the form with the evidence behind it. The various proprietary alternatives cost more and haven't demonstrated superiority. Three to five grams daily is the standard maintenance dose. Loading protocols saturate stores faster but aren't necessary; daily dosing reaches the same place in three to four weeks.
Timing is largely irrelevant, which is a rare piece of good news in this category. Consistency matters, daily dosing matters, the specific hour does not.
The caveats worth stating
Early concerns about kidney damage have not held up in people with normal kidney function across decades of study. That said, if you have existing kidney disease, this is a conversation for your own physician, not a decision to make from an article.
Creatine also causes some intracellular water retention, which typically shows up as one to three pounds on the scale in the first weeks. That's water in muscle, not fat, but it surprises people who aren't expecting it.
As a general rule, I'd rather someone fix their sleep, protein intake, and training before adding anything. But once those are handled, this is one of the few additions I think earns its place.