Serum hypomagnesaemia in an elderly day-hospital population

Serum magnesium concentration was measured in 223 elderly patients attending a day-hospital. Patients with medical conditions or receiving medication (other than digoxin/diuretics) which could affect magnesium levels were strictly excluded from the study. All patients were living in the community and were medically stable. Ninety-five patients were on no therapy whilst 107 were on diuretic therapy. In spite of strict exclusion criteria, 10.3% of patients on no therapy had serum magnesium levels below normal. There were 61 patients receiving a combination of frusemide and amiloride and 11.9% of these patients had below normal levels of serum magnesium. We conclude that there is a significant prevalence of unexpected hypomagnesaemia among Dublin inner city day hospital elderly patients. Significant serum hypomagnesaemia may still occur in patients on potassium/magnesium sparing diuretics.