Hi does anyone have any information regarding low vitamin D and what that can cause and what to do about it. Should one take vitamin D to increase it and for how long? My number is 18 which the docs say is low and that I need 2000 vitamin D daily? Are there risks? I don't take any vitamins and am in my early 50's so I reallly don't know anything about vitamins and supplements? Please any help would be appreciated.