Rise in serum calcium and magnesium concentrations after vitamin D administration in hypocalcaemic hypomagnesaemic magnesium deficiency.

A patient with hypocalcaemia and hypomagnesaemia secondary to small bowel resection and malabsorption was treated with synthetic vitamin D analogue, 1-alpha hydroxy vitamin D3. A prompt rise in serum calcium concentration and some days later a smaller and transient rise in serum magnesium concentration was observed. These changes in extracellular fluid composition presumably resulted from enhanced calcium and magnesium absorption associated with vitamin D activity.