Renin angiotensin aldosterone system inhibitors/antagonists/blockers (RAASi) are a cornerstone in treatment of patients with cardiovascular diseases especially in those with heart failure (HF) due to their proven effect on surrogate and hard endpoints. Renin angiotensin aldosterone system inhibitors are also the basis in treatment of arterial hypertension, and they are furthermore indicated to reduce events and target organ damage in patients with diabetes and chronic kidney disease, where they have specific indication because of the evidence of benefit. Renin angiotensin aldosterone system inhibitor therapy, however, is associated with an increased risk of hyperkalaemia. Patients with chronic kidney disease and HF are at increased risk of hyperkalaemia and similar to 50% of these patients experience two or more yearly recurrences. A substantial proportion of patients receiving RAASi therapy have their therapy down-titrated or more often discontinued even after a single episode of elevated potassium (K+) level. Since RAASi therapy reduces mortality and morbidity in patients with cardiovascular disease steps should, when hyperkalaemia develops, be considered to lower K+ level and enable patients to continue their RAASi therapy. The use of such measures are especially important in those patients with the most to gain from RAASi therapy.