Individuals with ESKD and treated with hemodialysis have a high mortality risk. Associative studies suggest a relationship between serum magnesium concentration and mortality risk. The influence of magnesium concentration on mortality risk is unknown. This pilot study will explore whether altering dialysate magnesium concentration in the presence of citrate will change serum magnesium concentrations.

To determine if a citrate enriched, Mg 1.0 mmol/L dialysate, when compared to a Mg 0,75 mmol/L citrate enriched dialysate leads to a:

• higher average serum predialysis total Mg on day 15 of the intervention
• higher average serum predialysis ionized Mg on day 15 of the intervention
• higher average serum postdialysis ionized Mg on day 15 of the intervention
• smaller proportion of patients with serum predialysis Mg <1,05 mmol/L on day 15 of the intervention
• larger proportion of patients with serum predialysis Mg > 1,50 mmol/L on day 15 of the intervention
• larger difference in predialysis Mg on day 15 versus day one of the intervention.

Inclusion Criteria:

1. Written informed consent must be obtained prior to any screening procedures
2. Clinically stable during two months prior to the study. This will be based upon clinical judgement.
3. On stable blood pressure medication 4 weeks prior to the study
4. Dialysis with a K3 dialysate
5. Adequate double-needle dialysis access (fistula or catheter)
6. Able to fill questionnaire/symptom score

Exclusion Criteria:

1. Predialysis calcium <1,9mmol/L during baseline
2. Magnesium predialysis >1,45mmol/L during baseline
3. Patient has a history of child C liver cirrhosis
4. Coronary intervention <3 months before randomization
5. Hospitalization <2 months before randomization
6. Uncontrolled predialysis hypertension >160/90mmHg despite 4 antihypertensive drugs
7. Predialysis blood pressure <90mmHg during baseline visit
8. History of dialysis access related problems <1 month before the randomization
9. Chronic Atrial fibrillation
10. NYHA class 4 heart failure
11. Any disorder, which in the investigator's opinion might jeopardise participant's safety or compliance with the CIP.

Participant-blinded, open to care providers and investigators