my levels were 5.8 - (!) extremely LOW. i was barely walking. i wanted to sleep all day long! i had chronic insomnia. my dr. prescribed 800 UI daily. after 8 months - still no results then i learned about "high" doses. started 30.000-50.000 ui. yes i was scared to do it and wanted to stop taking “So Much” this book and that there are scientific practical evidence for that i continued. thanks to this book my trust and confidence grew even bigger! now after 5 months my vit D level is 87! I took zahler 50k ui, (i think other brands also work well) now i feel like i am 15 y.o. - the level of energy i have now is unbelievable! thank you!