Ran across this dosage information this morning. John Campbell goes over some research.

https://www.youtube.com/watch?v=E3_t-EQIy0s

He talks about a group of 418 patients given large doses of supplement having vitamin d levels averaging 118, range of 74-384, and no adverse events.

From the paper "Long term supplementation with vitamin D3 in doses from 5,000 to 50,000 units a day appear to be safe".

Take the information for what it is worth from this one study.