I have been always low in vitamin d. And when I am low, my sleep cycle goes sideways (I am not sleepy at midnight). And when I am really low I have bone pain and wake up with my nails embedded in my palms. So since starting to read this site I started taking my vitamin d very regularly and big doses (2000 -7000 IU in the summer). I noticed that I was waking at 4am (after going to sleep at 11pm or midnight) and then having to nap mid morning. It wasn't too bad but weird (I am usually a night owl). I was also waking up with a start and heart pounding with anxiety. So I read all the advice here and ate nuts before bed, I took my vitamin d in the morning, and something else that I can't remember (I do a bunch of things every day and cannot remember which things go with which problems). I wasn't waking up with a start but I was still waking up early (I was now waking up between 3-5am). So I tried antihistamines, for a reason I cannot remember now (probably a thread here somewhere). I would sleep until 8am but was groggy for the whole day. Then something occurred to me, if sufficient vitamin d put me on a good sleep cycle maybe too much made me wake with the sun? So I cut back to 1000IU. And here I am waking up at 6:30-8am (usually 8 hours after bed time) and not requiring a morning nap. So does anyone know of a study linking vitamin d to extremely early waking? Has anyone else experienced this? If so, how do you adjust your vitamin D higher as the winter approaches?