My doctor recently tested me for Vitamin D among other things after I complained of minor gastrointestinal issues. A few months prior I had learned that my nummular eczema may be due to a Vitamin D deficiency. I had long wondered why the lesions were worse in the winter and all-but-disappeared in the summer. The Vitmain D test came back a bit below the "normal" range and my doctor recommended that I take a 1000 IU Vitamin D supplement.
I was pleasantly surprised to find a NYTimes article highlighting the scope of the Vitamin D problem. It seems to be quite widespread and serious; and not enough is being done to raise awareness and compensate for our lack of UVB exposure due to sunscreen and jobs and lifestyles which rarely take us outdoors during the peak exposure hours (10am-3pm).
I'm quite happy to have solved one more piece of the puzzle known as my body and I hope awareness continues to build. If you've never been tested for Vitamin D, consider asking your doctor to test you for it in your next visit.