http://www.naturalnews.com/049546_Grass ... iency.html
Vitamin D is one of the most basic and easily obtained nutrients in existence, yet millions of people today are grossly deficient in it.…
In order to know where you fall on the vitamin D range, it's important to get tested as a baseline. You can do this through your preferred doctor, or you can order a simple vitamin D test kit like this one offered by GrassrootsHealth: https://www.grassrootshealth.net/proj-welcome/?pr=95284
GrassrootsHealth has designed the D*Action Project, a study and analysis of research findings on vitamin D. A Vitamin D Testing Kit (Vitamin D*Action Testing Kit by GrassrootsHealth) is available through Dr. Mercola Premium Products for $65 (free shipping in US and Canada only). Registration in the D*Action Project is agreement to test vitamin D levels twice a year during a five-year study (which means a $65 a every six months).
http://shop.mercola.com/product/vitamin ... 90,0,0.htm
Today, many Americans are found to be in a serious deficiency state. Over 95 percent of senior citizens in the US may possibly be deficient, along with 85 percent of Americans. The late winter average vitamin D level was found to be about 15 to 18 ng/ml, which is far below optimal levels.