Frequency of hypomagnesemia in hypokalemic states.

Although both hypokalemia and hypomagnesemia have been linked with life-threatening cardiac arrhythmias, published studies disagree regarding the frequency of simultaneously low serum potassium and magnesium concentrations. To investigate the possible associations between the concentrations of these ions in serum, we carried out a retrospective study of all paired magnesium-potassium measurements reported from our laboratory during two separate two-week periods. Of 963 paired measurements in 421 patients, 12% of the samples were hypokalemic and 26% were hypomagnesemic. The frequency of hypomagnesemia was significantly greater in hypokalemic samples (38%) compared with nonhypokalemic samples (25%). The potential clinical importance of this relationship requires further investigation.