This effectively got my vitamin D levels up. I was told by a dietician that low D can make you feel as unwell as low iron, so I think the importance of this vitamin is understated. It also plays a part in glucose metabolism, apparently. I'm intolerant of many ingredients (intense allergy to dye, non-celiac gluten sensitivity, bloating from artificial sugars and other additives). No nausea, itchiness, bloating, or any discomfort from this product. I love it. By the way - this is a high dose, recommended by my endocrinologist (the dose, not the brand). You take it once a week, or you can do it twice a month. If you have darker skin or live in the north, you'll need more, but don't go crazy with this. You'll want to keep your doctor informed and have blood tests every so often