Are vitamins and supplements classified as complementary and alternative medicine?

To some, yes: As more and more conventional physicians familiarize themselves with the therapeutic use of vitamins & supplements, the less these things will be considered "alternative" and simply part of "good" medicine. Many physicians are now training in functional medicine (www.Functionalmedicine.Org) to learn how to effectively apply vitamins and supplements in treating chronically ill people.

Opinion: Vitamins are necessary for life and there are disorders and diseases associated with improper nutrition that are assessed by any competent physician. Supplements are usually compounds containing a nutrient or nutrients or other substances like an herb that may impact health or disease. More complementary practitioners prescribe nutrition but i would not classify that type of treatment alternativ.