25 micrograms (µg) of Vitamin D3 is absolutely fine for anybody. In fact rather on the low side for anyone with MS (but don’t forget there’s probably some in your multivitamin too). My neurologist recommends 50µg as the minimum we should be supplementing. Some people here are on doses many times higher still, although I don’t personally recommend that, as it is possible to overdose on the mega-high doses, and the symptoms are not dissimilar to those of MS itself, so not immediately obvious what you’ve done.
I’ve no idea what the recommended daily amount of magnesium is, or even if there is one. I take 750mg a day, in combined calcium and magnesium tablets (if you are supplementing Vit D, you should ideally supplement calcium too). I just buy ordinary over-the-counter strength from Boots, and take as instructed. I don’t know if I should be taking more or less,
Research is increasingly implicating low Vitamin D in the risk of relapse with RRMS, and possibly in the causes of MS itself. It’s not really understood whether people with MS have some problem making or absorbing Vitamin D in the first place, or just need a lot more of it for the ongoing repairs.
The theory is that adequate supplementation may reduce your relapse risk. It will not necessarily make you feel any better, so probably best to treat that as a perk you might get if you’re lucky, but not the main reason for taking it.
Magnesium may help with cramp and spasms, but unlike Vitamin D3, I’m not sure there’s any evidence it’s linked to reduced disease activity. So it’s just something that may help with symptom management, rather than actively affecting the disease.
Hope this helps.
P.S. Do you need to type in all caps because of vision problems? If so, fair enough, but if not, it looks a little bit shouty, and is hard to read.