4000 UI is recommended for adults by many doctors. https://vitamindforall.org/letter.html https://vitamindforall.org/letter.html I take 5000 UI D3 daily from

4000 UI is recommended for adults by many doctors. https://vitamindforall.org/letter.html https://vitamindforall.org/letter.html I take 5000 UI D3 daily from October to March and blood test are fine. I wouldn't take it during sunny times if you spend decent amount of time outside.