I've been taking 5,000IU of vitamin D3 daily for years because the doctor thought it would be beneficial. I've been assured that that dosage isn't considered excessive. So what they're talking about in this article must be a much larger dose.

From Multiple Sclerosis News Today (March 2), "ACTRIMS2020:
Vitamin D at High Dose Can Worsen MS, Early Study Says":

#ACTRIMS22 - Vitamin D at High Dose Can Worsen MS, Study Reports

I read that article a few days ago. I've been taking 4000 IU for about a year. I doubled the 2000 IU I had taken for years thinking it might help with my mood. It hasn't. I stopped taking vit D when I read that article. I suppose there is no coincidence about my worsening MS and the D?

According to this, 4000IU/daily isn't considered excessive. My doctor did say that the 5000/IU I've been taking isn't excessive either but I'm going to mention this article to her. I have a feeling it isn't excessive enough to matter.

Taking too much vitamin D can cloud its benefits and create health risks - Harvard Health

The mice in the study discussed in the Brain article were being given 75,000IU though I'm not sure if that was daily or weekly or what. If it was daily, that seems like a very jumbo-sized dose of vitamin D for a little mouse....

I don't think they know so very much about the connection between vitamin D and MS. They think that because many people with MS have low vitamin D levels, supplementing their vitamin D just might help, and there seem to have been some benefits for some people when they've been given additional vitamin D. But they're not sure. I like to think that the added vitamin D has been helping.

P.S. If you happen to get the NARCOMS newsletter called NARCOMS Now, I just received an issue of it (volume 8, #4, 2019), and there is a short article on pages 12-13, "Should People with MS Take Vitamin D? How Much and How Often?" Its information is from a paper presented at the ECTRIMS conference in September 2019, and it pretty much answers one of my questions about vitamin D--how much of it is too much?

Dr. Alberto Ascherio is affiliated with Harvard University's T. H. Chan School of Public Health. Dr. Ellen Mowry is a neurologist at Johns Hopkins University School of Medicine.

I take this to mean that 5,000IU/day is regarded as the maximum dose.

I read that issue but I probably didn't pay much attention to that article at the time. I'm going to go back to taking just 2,000 IU. I know of folks taking 10,000 daily or even 25,000 once a week.

That's what my doctor said too--that there are people taking far bigger doses of vitamin D than I've been taking. At least it's not expensive.