An interesting case that included visual hallucinations in a patient with severe hypomagnesaemia and hypocalcaemia.

A 57-year-old man presenting with profound visual hallucinations was found to have severe hypomagnesaemia and hypocalcaemia with a normal level of parathyroid hormone (PTH). Magnesium is essential to the release of PTH so the suspected pathophysiology was thought to be: low Mg → inappropriately low PTH → low Ca. He commenced supplementation and his symptoms resolved. Causes of hypomagnesaemia are discussed.