Vitamin D testing and treatment is a subject of controversial scienti c Discussions, and it is challenging to navigate through the expanding vitamin D literature with heterogeneous and partially opposed opinions and recommendations. In this narrative review, we aim to provide an update on vitamin D guidelines and the current evidence on the role of vitamin D for human health with its subsequent implications for patient care and public health issues. Vitamin D is critical for bone and mineral metabolism, and it is established that vitamin D De ciency can cause rickets and osteomalacia. While many guidelines recommend target serum 25-hydroxyvitamin D (25[OH]D) concentrations of ≥50 nmol/L (20 ng/mL), the minimum consensus in the scienti c community is that serum 25(OH)D concentrations below 25—30 nmol/L [10—12 ng/mL) must be prevented and treated. Using this latter threshold of serum 25(OH)D concentrations, it has been Documented that there is a high worldwide prevalence of vitamin D De ciency that may require public health actions such as vitamin D food forti cation. On the other hand, there is also reason for concern that an exploding rate of vitamin D testing and supplementation increases costs and might potentially be harmful. In the scienti c Debate on vitamin D, we should consider that nutrient trials Di er from Drug trials and that apart from the opposed positions regarding indications for vitamin D treatment we still have to better characterize the precise role of vitamin D for human health.