Reply To: New here. I just started taking 5000ui of Vit D3 on my own. Turning 44 this year :) I was having a round of cluster headaches. On my 3rd dose today. Cluster headaches are gone. not sure if it was the D3 or they were just done this time. I had my blood work done a couple years ago, and was prescribed Vit D for low levels. I live in Portland Oregon. ugg. no sun basically more than half the year. So, like i said, i just started taking the 5000ui daily again on my own. Perhaps there is a little bit of anxiety, possible irritability as side effects. I know, i need to get my l levels tested again. Just curious if its safe to just start on your own? Like i said, this is Portland Oregon after all.