Five guidelines recommended a supplementation of 400 to 800IU/d [21, 22, 27, 31, 33]six guidelines recommended 800 to 1000IU/d [16, 20, 23, 24, 28, 35]five guidelines recommended up to 2000IU/d [19, 25, 30, 37, 39]one guideline defined different doses for different subpopulations with ranges between 400 to 3000IU/d [5]and one third (10/31) did not define a dose and recommended an individual evaluation based on vitamin D levels, PTH levels (in case of X-linked hypophosphatemia), calcium levels, or symptoms of hypercalciuria. This evidence concerns the gene PTH and X-linked hypophosphatemia.