Proton pump inhibitors (PPIs) promote hypomagnesemia through loss of active Mg(2+) absorption via transient receptor potential melastatin-6 and -7 (TRPM6/7). Danziger et al. confirm the association of PPIs with hypomagnesemia in patients hospitalized at a tertiary medical center. They found that patients taking PPIs, compared with those receiving histamine-2 antagonists or no acid-suppressive medications, had a decline in serum Mg(2+) after adjusting for several clinical and laboratory factors. The effect was seen only in those concomitantly receiving diuretics.