I experimented with D3 supplementation up to almost a decade ago. I made some HN comments about it [2018]: https://news.ycombinator.com/item?id=17638508 https

I experimented with D3 supplementation up to almost a decade ago. I made some HN comments about it [2018]: https://news.ycombinator.com/item?id=17638508 https://news.ycombinator.com/item?id=17638508 I ultimately stopped it because it seemed to cause lower back aches. (Pretty sure, bone/muscle not kidney!) Every time I went on the D3, my back would start to hurt. That repeated several times, enough to suspect a pattern. The cause may be similar to the itchy, tingling teeth. According to this fascinating paper, Vitamin D can actually trigger the leaching of calcium out of bones, into circulation: https://pmc.ncbi.nlm.nih.gov/articles/PMC8147670/ https://pmc.ncbi.nlm.nih.gov/articles/PMC8147670/ After the abstract, find the section heading "Vitamin D mobilizes calcium from calcified bone". But that is in very high, pharmacological doses. Not your 5000 UI per day.