We read with interest the study by Galán et al “Impact of Serum Magnesium Levels on Kidney and Cardiovascular Prognosis and Mortality in CKD Patients” showing increased cardiovascular and all-cause mortality in relation to increasing serum magnesium (Mg) level in more than 700 subjects with variable levels of chronic kidney disease.1 One element that we felt was overlooked in this study was the lack of information on potassium (K) levels in the population studied, an electrolyte known to impact cardiovascular health and shares key mechanisms with Mg relative to cardiac electrophysiology.