The purpose of this trial is to examine the effect of increasing dialyse magnesium on serum calcification propensity in subjects with end-stage renal disease treated with haemodialysis.

Patients with end-stage renal disease (ESRD) have a 20-fold increased risk of cardiovascular mortality compared to the general population. Arterial stiffness, likely due to vascular calcification (VC), has been shown to predict cardiovascular mortality in ESRD. Serum calcification propensity (T50) is a novel biomarker, which is believed to reflect the propensity toward ectopic calcification (e.g. VC). Increasing serum magnesium (sMg) should increase T50, which might in turn reduce the formation of VC in patients with ESRD. A cheap and easy way of achieving this would be to increase the concentration of Mg in the dialysate (dMg) of patients with ESRD treated with haemodialysis (HD).

The investigators wish to conduct a randomised controlled double-blind clinical trial to examine whether increasing dMg will improve T50 in subjects with ESRD treated with HD.

Inclusion Criteria:

• Age ≥ 18 years.
• Treatment with maintenance haemodialysis for more than 3 months.
• Dialysate magnesium of 0.5 mmol/L (standard concentration).
• Serum magnesium < 1.2 mmol/L on average of previous measurements within the last 3 months.
• Women of childbearing age must be actively using contraceptive therapy (p-pills, estrogen depots or intrauterine device) as well as have a negative pregnancy test.
• Written informed consent.

Exclusion Criteria:

• Treatment with peritoneal dialysis.
• Parathyroid hormone > 66 ρmol/L.
• Previous parathyroidectomy.
• Current treatment with magnesium containing medication or supplements.
• Other diseases or conditions, which, in the opinion of the site investigator, would prevent participation in or completion of the trial.
• Pregnancy or breastfeeding.