As far as I understand Vitamin D3 has no direct physiological effect but has to be first converted. If a person if given a mega-dosis. (50000-200000 IU) of Vitamin D3, how long does it take till the body produces a physiological response? Is it a matter of hour? Is it a matter of days?

  • $\begingroup$ This sounds like an upstream question... i.e., you want to know this in order to know something about what happens if someone takes a large dose of vitamin D3. Can you flesh out your question? $\endgroup$
    – De Novo
    Jul 5, 2018 at 23:48
  • $\begingroup$ @DanHall I changed the question to be a level higher upstream. $\endgroup$
    – Christian
    Jul 7, 2018 at 21:41
  • $\begingroup$ I not sure we still don't have an X-Y problem here. Is this actually the thing you're trying to figure out? Or some thing that you are trying to find out in order to answer a different question. I'm making an attempt to answer, but give me a minute, since a quick search has shown one of my assumptions (that nobody would study that large a dose) to be false. $\endgroup$
    – De Novo
    Jul 8, 2018 at 16:53
  • $\begingroup$ Well, it turns out I don't know the answer to your question, and I'm not comfortable offering an authoritative answer just by reading some new literature. In a different context, a patient with Vitamin D deficiency, it will take 3+ weeks before calcitriol levels normalize in response to oral Vitamin D3. That (normalized levels of calcitriol) is the physiologic response to oral Vitamin D3. The response to mega doses would likely be different, but I don't know what it would be. There's some work out there, but you'd have to draw some conclusions yourself. $\endgroup$
    – De Novo
    Jul 8, 2018 at 17:05


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