Reply To: What could be causing my body's inability to sustain vit d? My celiac is under control. For past 4 years my vit D will hit 60 if on the super prescription dose of 50,000. Then, when off the prescription and on Vit D 4000 per day, my level drops to 15-22 . This has been my roller coaster ride for over the past 4 years. My calcium is normal to high. I have osteoporosis. 52 year old female, Caucasian, normal weight about 120 So far my internist, Gastro, and rheumatologist are all stumped. So they just keep giving me the prescription dose to boost me. My body cannot sustain it. What could cause this? Is there something different that I could do to get better results? Your comments are much appreciated. Kindest regards.