Why You May Not Need That Vitamin D Test After All.

Right now, at this very moment, your vitamin D levels are probably at their lowest levels of the year, since your body can't make the nutrient from sunshine during the dark winter months. You could be facing an increased risk of heart disease, osteoporosis, dementia, diabetes, and a variety of cancers. Scared yet? Many people are, especially after having their levels tested and being told that they're deficient. With a spate of recent studies touting the prevalence of D deficiency—half of all Americans—and the disease–prevention benefits of having high vitamin D levels, doctors have rushed to test and treat low levels with supplements.