Randomized placebo-controlled interventional trial to investigate the effect of oral magnesium supplementation on intracellular magnesium in subjects with chronic kidney disease. We hypothesize that oral magnesium supplementation will increase intracellular magnesium in subjects with chronic kidney disease as well as increase serum magnesium.

Chronic kidney disease (CKD) is associated with increase cardiovascular morbidity and mortality independent of traditional cardiovascular risk factors due to increased vascular calcification. Epidemiological and experimental data suggest that hypermagnesemia and magnesium supplementation reduce vascular calcification in chronic kidney disease by increasing calcium/phosphate solubility in serum, by inhibiting calcium influx into vascular smooth muscle cells (VSMC), by inhibiting intracellular pro-calcification enzymes in VSMC and by increasing activity of intracellular anti-calcification enzymes in VSMC. A trial to investigate the effect of oral magnesium supplementation on vascular calcification in subjects with CKD is currently being planned, but prior to initiating such a trial it is necessary to determine the dose of oral magnesium needed to increase intracellular magnesium and serum magnesium.

Inclusion Criteria:

• Estimated Glomerular filtration rate (eGFR) < 60 mL/min.
• Serum magnesium < 0.82 mmol/L.
• Written informed consent.

Exclusion Criteria:

• Hemodialysis.
• Peritoneal dialysis.
• Kidney transplant recipient.
• Parathyroid hormone > 600 pg/L.
• Pregnancy.
• Comorbidity that makes study participation and completion impossible.