PTH and osteoporosis: We recommend to maintain 25(OH)D levels above 30 ng/mL (75 nmol/L) in subjects:With osteopenia, osteoporosis or fragility fractures;On treatment for osteoporosis;Who belong to at risk categories (see Section 3.1).We suggest to consider serum PTH measurement when vitamin D values are lower than 30 ng/mL (75 nmol/L), particularly if tested in Summer and Autumn.