Vitamin D is a fat-soluble vitamin that is essential for human health. It regulates calcium and phosphate homeostasis and is therefore vital for musculoskeletal functioning. In the UK, up to 50% of the adult population may be vitamin D insufficient following the winter months, with one in six being severely deficient. In this podcast, Dr Roger Henderson looks at who is most at risk of vitamin D deficiency, how it should be diagnosed, what treatment options are available and why unlicensed vitamin D preparations should not be recommended.