Treatment failure and vitamin D deficiency with 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3

A formulation comprising 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, or a combination of 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3, for use in the treatment of insufficiency or deficiency of 25- hydroxyvitamin D, or a disease associated with deficiency of 25-hydroxyvitamin D in a patient, wherein the formulation is provided as an oral formulation of a sustained release dose and wherein the 25-hydroxyvitamin D2 and / or 25-hydroxyvitamin D3 is provided in inside a waxy matrix and included in a coating material.