The current high-sodium, low-potassium diet contributes to the high prevalence of high blood pressure (hypertension). Indeed, the anti-hypertensive effects of potassium supplementation are well-established. Hypertension is even more prevalent and resistant in patients with chronic kidney disease (CKD) and contributes to further decline in kidney function. Four recent epidemiological studies (published 2014 - 2016) showed that higher dietary potassium intake was associated with better renal outcomes. All studies recommended an intervention study with potassium supplementation in patients with CKD, but this has not been performed. The aim of this study is to study the renoprotective effect of potassium supplementation in patients with CKD (stage 3b or 4, i.e. estimated glomerular filtration rate [eGFR] 15 - 45 ml/min/1.73 m2).

Inclusion Criteria:

• CKD 3b or 4 (45 - 15 ml/min/1.73 m2)
• Δ eGFR (as estimated by the CKD-EPI equation) > 2 ml/min/1.73 m2/year (in preceding ≥ 1 year with at least 3 measurements)
• Hypertension (defined as office blood pressure > 140/90 mmHg or use of anti-hypertensive medication)

Exclusion Criteria:

• Hyperkalemia (serum potassium > 5.5 mmol/l) at study visit V0
• Medical reasons to continue dual RAAS-blockade, mineralocorticoid receptor blockers, potassium-sparing diuretics, or oral potassium binders.
• Patients with previous history of ventricular cardiac arrhythmia
• Patients with a life expectancy < 6 months
• Expected initiation of renal replacement therapy < 2 years
• Incapacitated subjects
• Women who are pregnant, breastfeeding or consider pregnancy in the coming 2 years.