I have had brain fog for over 3 yrs and had every test done and all are normal. I feel like I drank a beer or two, spaced out but all the time non stop. I can still go to work and drive ( which can be tough) I have had other symptoms but my biggest one is this light headed feeling. I found out I am at 15 with my Vitamin D and started taking 50, 000 2 times a week. I just started. My questions is do you think the light headedness is from the lack of Vitamin D and how long do you think till I feel better.?