[westwing]

If you take 10,000IU because 8895IU is what gets 97.5% of people to 50nmol/L, you are basically assuming you need more supplement than 97.5% of people, which is highly unlikely. There are people "at risk" that have trouble metabolizing the supplement, but chances are you're not one of them.

You need to do blood tests. Don't take 10,000IU daily without consulting a doctor. The "generally considered safe" upper limit is 4000IU. You'll probably be fine with 2000IU. Too much Vitamin D can mess with your calcium and doses as low as 5000IU/daily over a few years have been reported to cause serious problems.