I was too low on D3 on 400 units a day (no surprise, but I was ignorant). Then at 800 units a day, I was still too low on blood test. Last test, at 1600 units, still too low. Don't know if I'll ever get up to normal (forget what my number was, but it was not what it should be. I get NO sun, as I cover up with sun resistant fabric head to toe. That makes it more of a challenge. But I am upping the dose to 2000 units a day. I am aware that the hormone effect could be a problem.