Many diuretics cause hypermagnesiuria which may lead to magnesium deficiency, presenting as hypomagnesaemia, cardiac arrhythmias and tetany. Loop diuretics cause hypermagnesiuria mainly through direct blockade of magnesium reabsorption at the loop of Henle. Distal tubular diuretics block magnesium reabsorption at the distal convoluted tubule and also reduce magnesium reabsorption at the loop of Henle by an indirect mechanism.