That seems low, considering that 5000iu softgels are very readily available (eg the vit D supplements at Costco).

Edit: acute toxic dose not established, chronic toxic dose >50k iu/day. https://www.medscape.com/answers/819426-102369/at-what-dose-...

Edit2: this article lists 4000 IU/day as the generally recognized as safe level https://www.healthline.com/nutrition/vitamin-d-side-effects#...