Vitamin D Deficiency

I really enjoyed Anna Lea Roof's Article on Vitamin D deficiency. I am guessing that it is far more common than people realize. Especially during the winter months in the Northern states where we go to work in the dark, leave work in the dark and don't get outside during the lunch hour even if it is sunny and warm. Does anyone else have any knowledge/experience with Vitamin D deficiency? For you doctors out there, is this something that you would test for as a matter of course or are vitamin deficiencies the long forgotten diagnosis? I would be interested in finding out why and how Anna's doctor was able to diagnose the deficiency since in her article she states that at the time she felt fine.