It varies by the individual. My personal limit is 3000 IU daily without experiencing hypercalcemia. One of the symptoms is whole bone pain. I stick with 2000 IU and that is not every day. In my case, it was right thigh bone, a left ulna, and finger bone on left hand. It leaches calcium out of your bones and drops it in your bloodstream. The main ingredient in rat/mice poison if anyone wants to look it up. That is the mechanism of their death. MORE is not better.
“My personal limit is 3000 IU daily without experiencing hypercalcemia.”
Mine is somewhere above 5,000. I also take vitamin K.
“Vitamin D promotes the production of vitamin K-dependent proteins, which require vitamin K for carboxylation in order to function properly. The purpose of this review is to summarize available evidence of the synergistic interplay between vitamins D and K on bone and cardiovascular health....Current evidence supports the notion that joint supplementation of vitamins D and K might be more effective than the consumption of either alone for bone and cardiovascular health.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613455/
“No strong evidence proves that moderate amounts of vitamin D are harmful without an adequate intake of vitamin K. However, research is ongoing, and the picture might become clearer in the near future.”
https://www.healthline.com/nutrition/vitamin-d-and-vitamin-k#TOC_TITLE_HDR_4