How much are you taking? As above the new recommendation is a minimum of 1,000 IU/day and if you're deficient to begin with you need much more. They've also been studies that with the D you need at least 1200-1500 mg of calcium and anywhere from 1/2 to the same amount of magnesium. Taking less than you need or not "filling your tank" when you're already deficient before going on maintenance dose doesn't do you much good.