This is how I found my 10k IU of vitamin D a day, based on modern recommendations for indoor workers, that I modulate based on how much I'm outdoors, was perfectly on the mark!
Also an indoor worker. 10K IU daily would have put me far into hypervitaminosis D range.
Make sure you test after a very long time, such as a year of steady supplementation. A lot of the excess Vitamin D cases were taking less than 10K IU daily.
This is the entire issue. You get vitamin D from the sun. The concept of "steady supplementation" of vitamin D is not logical, unless your sun exposure is also steady, which is where the not-so-useful guidelines come from: some mean of some distribution of some skin tone of sun exposure, leaning on the "less" side of things, with current recommended values based on means from over 50 years ago.
I would never take 10k steady, because I don't live in a cave!
This is the amount I shoot for in the winter - I live in New England - it's made a huge difference in my life. I'm totally open to it being placebo though and I don't care. I don't supplement with it during the summer.
Make sure you test after a very long time, such as a year of steady supplementation. A lot of the excess Vitamin D cases were taking less than 10K IU daily.