SGLT2 inhibitors increase low serum magnesium levels in patients with chronic kidney disease immediately after treatment.

Background: Sodium-glucose cotransporter 2 (SGLT2) inhibitors have been shown in clinical trials to increase serum Mg²⁺ levels in patients with type 2 diabetes mellitus. However, it is unclear whether this effect is similarly observed in patients with chronic kidney disease (CKD) and whether such an increase is observed immediately after treatment.

Methods: Our retrospective observational study included the 62 patients with CKD who started SGLT2 inhibitor therapy at our institution between 2017 and 2022 and who had complete data on serum Mg²⁺ measurements at baseline and at 1, 3, and 6 months after treatment. Patients were divided into three subgroups, stratified by serum Mg²⁺ levels at baseline. We evaluated the changes in serum Mg²⁺ levels from baseline to 6 months after treatment and the factors associated with these changes.

Results: Median eGFR and mean serum Mg²⁺ at baseline were 33.5 mL/min/1.73 m² and 2.03 mg/dL, respectively. Treatment with SGLT2 inhibitors significantly increased serum Mg²⁺ levels immediately from 1 month after treatment compared with those at baseline and persisted over 6 months, with an overall mean change of 0.13 mg/dL from baseline to 6 months. This increased effect was observed in the low and middle tertile subgroups, but not in the high tertile subgroup. Multivariate linear regression analysis revealed that baseline serum Mg²⁺ levels and sodium-chloride differences, as a parameter of acid-base status, were independently associated with these changes.

Conclusions: SGLT2 inhibitors increased serum Mg²⁺ levels in patients with CKD, particularly those with lower baseline Mg²⁺ levels, potentially improving their prognosis.