From the University of Washington comes the info I present on this 5 minute video on Vitamin D3 or Cholecalciferol.  It is called the sunshine vitamin.  You will see why in the video.  Problem is most of us do not get enough sun, some of use due to age (>70) don’t make it well and some of us have pigmented skin so we need more time in the sun to make adequate amounts.

This video should answer some questions for you:

1. How do I know if I have enough Vitamin D?
2. What do you measure to find out?
3. How much should I take?
4. How is Vitamin D made within my body?