The many recently published data on
vitamin D have raised much interest in the medical community. One of the consequences has been a great increase in the prescription of
vitamin D concentration measurements in clinical practice. It must be reminded that only the measurement of
25-hydroxyvitamin D (25(
OH)D) concentration is indicated to evaluate
vitamin D status. Furthermore, since
vitamin D insufficiency is so common, since treatment is inexpensive and has a large safety margin, and since we already have much data suggesting that besides its classic effects on bone and
mineral metabolism,
vitamin D may potentially be helpful for the prevention/management of several diseases, perhaps should it be prescribed to everyone without prior testing? In our opinion, there are however groups of patients in whom estimation of
vitamin D status is legitimate and may be recommended. This includes patients in whom a "reasonably" evidence-based target concentration (i.e., based on randomized clinical trials when possible) should be achieved and/or maintained such as patients with
rickets/
osteomalacia,
osteoporosis,
chronic kidney disease and kidney transplant recipients, malabsorption,
primary hyperparathyroidism, granulomatous disease, and those receiving treatments potentially inducing bone loss. Other patients in whom
vitamin D concentration may be measured are those with symptoms compatible with a severe
vitamin D deficiency or excess persisting without explanation such as those with diffuse
pain, or elderly individuals who fall, or those receiving treatments which modify
vitamin D metabolism such as some anti-
convulsants. Measurement of
Vitamin D concentrations should also be part of any exploration of
calcium/
phosphorus metabolism which includes measurement of serum
calcium, phosphate and PTH.