Summary

A 59-year-old lady presented with vomiting and diarrhoea. She was found to have severe hypercalcaemia (5.2 mmol/l) and to be in renal failure. She had a high daily intake of calcium carbonate in the form of Rennies Dual Action, raising the possibility of milk-alkali syndrome. She had ongoing gastrointestinal symptoms after resolution of hypercalcaemia. Further investigation revealed, previously undiagnosed rectal Crohn's disease. Serum 1,25-dihydroxyvitamin D (calcitriol) level was markedly elevated. It is possible that the calcitriol from Crohn's disease tissue facilitated excessive absorption of calcium from the antacid preparation, thus triggering hypercalcaemia.