Frequently patients who are low in vitamin D, as determined by a blood test, get put on high doses of prescription vitamin D2 (also known as ergocalciferol) by their physician. However, according to the world’s leading vitamin D experts, vitamin D2 is much less effective than Vitamin D3 (also known as cholecalciferol) in humans. The authors say “Physicians resorting to the use of vitamin D2 should be aware of its markedly lower potency and shorter duration of action relative to vitamin D3″. How do you know if you need vitamin D3 supplements? Ideal blood levels of vitamin D 
are between 50-80 ng/ml. This is not always the same range as what is indicated on typical lab reports which can go as low as 30 ng/ml. If you are under this optimal range, you may benefit from anywhere between 1,000-5,000 IUs of vitamin D3 daily. To know for sure, call us at 517-290-6041.
Source: Armas L, Hollis B, Heaney R. Vitamin D2 is Much Less Effective than Vitamin D3 in Humans. The Journal of Clinical Endocrinology and Metabolism.2004; Vol 89: pg 5387.