I do not know if anyone had researched on the subject. VIDEO: http://www.worldstarhiphop.com/video...YWX4lFW4Ptq2F1 The more interesting. I recently did a blood test to identify vitamin and Vitamin D coincidentally appeared as insufficient. 21.7ng/ml while sufficient levels are between 30.0 ng / ml and 100.0 nl / ml. :unsure: 1 week ago I'm taking 20.000UI of vitamin D per week to climb my blood level and after a few weeks I will do another blood test. I have never done a survey of vitamin D, and maybe I'm already there years with this failure. The funny thing is that I take the multivitamin GNC Ultra Mega Man and it says it has 400% vitamin D. Do some people have difficulty metabolizing this vitamin, even doing the intake the same?