I had lunch with my best friend today and learned she like myself suffers from low levels of vitamin D. Her levels are so low she takes a high dose once a week (prescription). My levels are not that low (40 ng/ml) but was advised by my endocrinologist to up my oral intake. Prior to my recent test I was taking 600 IU in my Ca/Mg/Vit D supplement plus the 400 IU in my multi-vitamin not to mention my hours in the sun (I don't use sunscreen - I know this is bad). I have recently added 1000 IU vitamin D supplement but will not repeat my blood work until Jan. 2009. We both consume a lot of dairy products on a daily basis. Both of us were shocked by our recent blood test results. We both were confused by our low levels given the current factors (prescription for her, oral supplements, sun exposure, etc). Are there factors, situations, foods, etc which block the absorption of vitamin D?