Forgotten electrolytes: magnesium and calcium flux during dialysis

PURPOSE OF REVIEW: Calcium and magnesium remain incompletely individualized in contemporary dialysis prescriptions despite growing evidence linking their concentrations to cardiovascular outcomes, vascular calcification, mineral metabolism, and mortality. The 2025 Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference report on chronic kidney disease (CKD)-mineral and bone disorder (MBD) and recent kinetic studies of intradialytic ion fluxes make a focused review of these "forgotten" divalent cations timely. RECENT FINDINGS: Intradialytic calcium mass transfer is influenced by patient- and prescription-level factors, and total serum calcium incompletely reflects biologically relevant calcium flux; ionized calcium may decline during dialysis as hemoconcentration increases albumin concentration and alkalosis increases albumin-bound calcium. Small randomized trials show that raising dialysate magnesium improves serum resistance to calcification, but whether higher dialysate magnesium improves clinical outcomes remains unknown. The 2025 KDIGO report retains the 1.25-1.50 mmol/l dialysate calcium range and identifies individualized calcium mass-transfer assessment as a research priority. Dial-Mag, a large pragmatic trial comparing higher versus conventional dialysate magnesium concentrations, is ongoing. SUMMARY: Recent evidence challenges the assumption that standardized dialysate calcium and magnesium prescriptions are optimal for all patients. Future studies should define patient-specific targets, validate practical methods to assess peridialytic calcium and magnesium levels and intradialytic flux, and determine whether individualized dialysate prescriptions improve clinical outcomes.