Causes of Vitamin D Deficiencyby
that may cause a person to become deficient in vitamin D.
Cystic fibrosis (CF... soluble vitamins, particularly vitamin D.
Crohn's disease causes the lining...
and ensuring that all the ingredients are natural vitamins rather than a synthetic version could help also.
Also have a look (if possible) what the tablet is made from, filler, etc. can sometimes causeskin reactions.