Some doctors will prescribe it for off-label use, but this is pretty rare. It's possible to purchase it from overseas websites as it is not scheduled, but this is technically not legal, and it will still cost quite a bit out-of-pocket. With that said, it can definitely be potentially dangerous, and dosing+frequency would have to carefully be paid attention to, as well as monitoring results via blood tests imo, and having done extensive research and so on. I wouldn't suggest anyone just purchases it to experiment with it without being very careful and having a high appetite for risk. But other things like glycine or spermadine or vitamin D or magnesium I'm much happier to gleefully suggest to people.
I personally don't buy that NR does much. I think there's some interesting hints that we're getting close to finding out useful things, but I haven't found much that personally convinced me about NR and those related to it. Agree with what I hear on podcasts like Peter Attia about it, but I think maybe some day soon we'll find something promising in that area.
It's a hard area to give advice in since everyone is different, so I can't really offer much besides that I think for the best return, someone has to spend a lot of time doing their own research and testing and so on to find out what works for them
