The 25-hydroxyvitamin D (25OHD) serum concentration should not be measured to everybody but recommendations for this measurement in several clinical situations are available from numerous guidelines and expert positions. It can be proposed to measure 25OHD in diseases where a target range of 25OHD concentrations associated with better outcomes is defined with a sufficient level of evidence, and when this target concentration is difficult to reach without previous measurement (or may be exceeded in case of too large doses are provided). Many National and International Medical Societies recommend to measure 25OHD at least in any situation of « bone fragility » (defined by a low bone mineral density and/or a low energy fracture), in malabsorptions, in chronic kidney disease, in any « phosphocalcic pathology, in patients with clinical signs of profound vitamin D deficiency or excess, and, more generally in any biological exploration of calcium/phosphorus metabolism that includes the measurement of PTH. Although these recommandations may seem discordant with the recent French restriction in the reimbursment of 25OHD measurement, they may still be reimbursed.