Hi Janet, Thanks for the question. Vitamin D3 is necessary for absorbtion of calcium, which is why calcium supplements also contain D and yes if your dr. advises it you should take it. This link (written by Pam, a very smart lady) will tell yoiu about D3, what it does, how much is needed and why you should take it. Take care...phyllis
http://www.healthcentral.com/osteoporosis/c/question/734843/62265