Creatine comes from red meat in your diet. Your body absolutely evolved for dietary creatine to exist.
Creatine is the most studied studied supplement and everything shows that unless you have kidney issues it is all upside.
Discussion
Yeah. I'm not aware of any issues with creatine dosing. (Not that there aren't for decently healthy people, just that I don't know.)
I’m not aware of rebound issues but it is my understanding that your body generates creatine from red meat but if you dose creatine, for the time that you are on it, your body stops producing it, so you don’t get incremental, you need to dose for that. And if you stop taking it my understanding is your body starts producing creatine again. My strong suspicion is it’s the same with melatonin the only question is if there is a lagged effect with either and how long. My belief is the lagged effect for creatine is small enough to not be measured in studies so yeah seems like no bad effects. I haven’t looked into the lagged effect of melatonin yet if any.
Sleep is so important to your overall health. For me, I take melatonin and don't worry about the risks.
I looked at the what if and maybe of taking it and compared to the definite shitstorm of chronic sleep deprivation and for me it is a no question win.
Each person has to do that math on their own. How disrupted is your sleep, for how long, why, how likely is it to get better without melatonin? My sleep was really bad and the damage from sleep deprivation was piling up quickly.