I do 10000iu 2-3x a week.
Back in my night shift life, I was at 8000+/d to get into the higher spectrum of the 25-OH blood test that your doctor can administer.
I’d suggest everyone to get tested. It’s free, an approved AHS test. Docs just don’t give it because $$, but if you ask they will.
Say you work nights.
"The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents... some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the light into the peace and safety of a new Dark Age."
-H.P. Lovecraft