Several questions remain to be elucidated, such as the identification of the VDR-vitamin D complex in the nucleus, the mechanisms of vitamin D regulation, the role of the 24-hydroxylase (CYP24A1) that breaks down the active form of vitamin D to an inactive form in patients with TB and T2DM, and oral supplementation with higher concentrations of 25(OH)D3 than those evaluated so far. Here, CYP24A1 is linked to type 2 diabetes mellitus.