Recent research is clear that in our climate and northern location, we are likely all in need of additional Vitamin D, even in the summertime! D3 is the most active form of Vitamin D that your body uses best. Taking a regular Vitamin D supplement is encouraged by most health care practitioners and it is a safe and effective way to help with things like immune system function, heart health and bone health. Taking a daily supplement is recommended at 1000IU per 50 pounds of body weight (or more as recommended by your physician if blood measured levels are lower).