At 10,000 IUs a day my Ca+ levels are high/normal on blood tests 3x yr.
Any more than 10K of Vit D3, and I'd start taking K2 of the mk4 type at 1000mcg or 1 mg per 10,000 UIs Vit D3.
If you want to dive into this a good (cheap) book is Jeff T. Bowles "Vitamin D3"