That’s over double the dose considered “safe”. Obviously, I’m not suggesting you do otherwise; it’s just way outside the bounds of what most adults would do unless directed to by their physician.
The neat thing about vitamin D synthesis in the skin is that it stops once there's enough of it - it is literally impossible to overdose on vitamin D through sun exposure. So, there's a ceiling that makes "must be higher in sunny regions" far from obviously true!
That gets stored in the fat. Overdose through ingestion is a thing, our bodies aren't so smart about that; it's skin synthesis specifically that limits itself.
I’m prescribed 50,000 3x a week. The RDA was possibly miscalculated, but the only real way to know what will work for you is test - dose - test, repeat.
https://www.ncbi.nlm.nih.gov/pubmed/19667143
Must be much higher in sunnier regions.