Vitamin D3 is a form of this vitamin that is rapidly converted in the body ready for use. Although well known for its role in maintaining healthy bones, more recent research has shown that Vitamin D has many more functions in the body. Vitamin D is needed for the normal absorption of calcium and phosphorous and for normal blood levels of calcium. Vitamin D is required for normal maintenance of bones and normal muscle function. Note: This product is not intended to diagnose, treat, cure, or prevent any disease, nor should supplements be used as a substitute for a balanced diet. Not intended for pregnant/breastfeeding mothers or children under 18. Do not exceed the recommended dose.