Risk of hypermagnesemia in patients with eating disorders taking magnesium oxide preparations: a retrospective study

This study examined the incidence of hypermagnesemia in patients with eating disorders, its associations with renal function, body mass index, and magnesium oxide use, and the correlation between different methods of estimating renal function and serum magnesium levels.

This retrospective cohort study was conducted in female patients with eating disorders treated at Nagoya University Hospital between January 2018 and December 2022. Patients diagnosed as eating disorders, based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision, were included. Serum magnesium levels, estimated glomerular filtration rate, body mass index, and magnesium oxide prescriptions were collected. Linear mixed-effects models were used to analyze factors affecting serum magnesium levels. Renal function screening methods were compared in underweight patients.

Among 194 patients, 42 (21.6%) developed hypermagnesemia (≥ 2.5 mg/dL; maximum 5.3 mg/dL). Younger age, lower body mass index, and reduced estimated glomerular filtration rate were linked to higher magnesium levels, whereas magnesium oxide use showed no clear association. Further analysis showed that the alternative estimated glomerular filtration rate method, adjusted for body size, negatively correlated with elevated serum magnesium levels in underweight patients.

The incidence of hypermagnesemia in patients with eating disorders receiving magnesium oxide was comparable to previous studies. Risk factors include low body mass index, impaired renal function, and younger age. Although monitoring is warranted, severe complications were not observed, suggesting magnesium oxide need not be avoided. The use of body size-adjusted estimated glomerular filtration rate may improve the screening for hypermagnesemia in underweight patients.

Level III, well-designed cohort or case-control analytic studies.