- Mayo Clinic says "Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity."
- news-medical.net says "To prevent toxicity, tolerable upper intake levels have been fixed for vitamin D as..." 4000 for adults.
- healthline.com says "A daily vitamin D intake of 1000–4000 IU (25–100 micrograms) should be enough to ensure optimal blood levels for most people."
https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...
https://www.news-medical.net/health/Vitamin-D-Overdose.aspx
https://www.healthline.com/nutrition/how-much-vitamin-d-is-t...