Yes - a blood test called 25-hydroxyvitamin D, which, though expensive ($20 to $100 a pop), is covered by insurance. Your level should be at least 30 nanograms per milliliter of blood and not more than 100. If your level is way below that, say around 18, you need to take 1,200 international units or more a day of vitamin D supplements, either the type called D2 or D3, said Dr. Michael F. Holick, an endocrinologist and leading vitamin D researcher at the Boston University School of Medicine. Continue Reading…
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