A2: If you look at the 1,25 dihydroxy vitamin D, you could get the false impression that there's too much vitamin D, as it can go high when there is a vitamin D deficiency (as well as other conditions). 25 hydroxy vitamin D will get you the storage form of vitamin D and is the appropriate test. Vit D3 is better then D2 (which is synthetic, has a shorter half-life, and doesn't stimulate the vit D receptors quite so well, but can do in a pinch), and I'd be nervous about going over 5,000iu daily without a good reason. The 50,000iu tabs are more for weekly or monthly dosing. Vit D3's half life is about 2 weeks, so weekly dosing is certainly reasonable. Always a good idea to check levels before starting and after 6 half-lives (3 months).
Dr. Malcolm Sickels, MD
210 Little Lake Drive, Suite 10
Ann Arbor, MI 48103
http://drsickels.com