Creatine is one of the very few supplements that seems to have only upsides and few if any side effects (except the basically obligatory "minor stomach upsets for some people" ). You can take it every day at any time of day, the effects take a few weeks to build up.
The main downside is that the effects are small - most of the research is in strength and endurance training and it seems like at most there's a 5-10% increase in lifting endurance (IIRC, it's been a while since I researched this).
It's one of a very few supplements that I personally feel should be generally taken by most people (unless you eat a lot of red meat).
The others are omega 3 (unless you eat fish several times a week) and possibly magnesium as the western diet tends to be low in that.
If you want to read more about effects of creatine on the brain this is a good paper:
The consensus seems to be that supplementation of creatine is less clearly linked to increases in the brain than it is for muscle (although there have only been limited studies done), however, if you've ever suffered from depression, sleep deprivation or other neurological issues it's likely to be beneficial. For people without those issues, there's less evidence yet, but they would still get the benefit of more energy overall if not specifically more cognitive energy.
Creatine is awesome, but hair loss in men with male pattern baldness is frequently reported by myself and others in comments under all the "creatine is amazing no downsides" youtube posts and elsewhere. I've experienced it personally.
It could be that men who feel the need to start taking creatine are at the point in life where baldness is likely to occur, are taking other supplements that could be testosterone converting, are exploring these options as part of an unconscious recognition of an onset of balding, or are just becoming aware of existing balding due to greater self-awareness due to their self-improvement.
I'd put any one of those ahead of "creatine made me go bald".
The link to baldness comes indirectly through increasing DHT. The increase in DHT, if I understand right, can speed up existing hair loss. Where it gets shaky is that DHT is also increased by excersize and follow-up studies accounting for that found a decrease in DHT while on creatine. So we don’t know yet, basically, and you should stop if there is a concern.
The caveat is finding a high-quality supply of creatine. So many on-line reviews for once great brands of creatine powder talk about how those brands recently switched to a new supplier, how the consistency changed to that of powdered sugar, and how all of a sudden they were getting major gastrointestinal problems from a brand that used to be good.
It's hard to know where to go for the right kind of supplement. I've taken it as an exercise supplement in the past with no seeming downsides, but in a few hours search, I couldn't find a supply that doesn't have dozens to hundreds of these complaints against it.
Kre-Alkyn on Amazon has a patented method of getting it past the stomach acid which I’ve found, over many, years, removes the bloating issues with monohydrate (most common)
I don't know your dosage and use case but under creatine loading (5+ grams/die), water weight and bloating becomes a very, very noticeable side effect (in responders).
afaik that's temporary and lasts only a few weeks, even if maintaining the loading dose.
The effect also seems localized to muscles so unless you are overweight the effect is mostly flattering.
I originally put it in, along with vitamin c during flu season, but felt I haven't personally done enough research to make claims about them. Regarding vitamin d, I am unsure about whether it should be taken with vitamin k or not.
The main downside is that the effects are small - most of the research is in strength and endurance training and it seems like at most there's a 5-10% increase in lifting endurance (IIRC, it's been a while since I researched this).
It's one of a very few supplements that I personally feel should be generally taken by most people (unless you eat a lot of red meat).
The others are omega 3 (unless you eat fish several times a week) and possibly magnesium as the western diet tends to be low in that.
If you want to read more about effects of creatine on the brain this is a good paper:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7916590/
The consensus seems to be that supplementation of creatine is less clearly linked to increases in the brain than it is for muscle (although there have only been limited studies done), however, if you've ever suffered from depression, sleep deprivation or other neurological issues it's likely to be beneficial. For people without those issues, there's less evidence yet, but they would still get the benefit of more energy overall if not specifically more cognitive energy.