An increase in blood-serum-potassium levels (hyperkalemia) is common in patients with renal impairment or heart failure. Indicated drug treatments, namely RAAS-inhibitors, (RAASi) such as ACE inhibitors, AT1 receptor-antagonists and aldosterone-blockers, lead to a further rise in potassium levels and may need to be discontinued despite their favourable cardiac and renal effects. Patiromer is an oral drug that can be used to treat latent/chronic hyperkalemia, reduce the risk of acute episodes of hyperkalemia, and enable the continuation of RAASi treatment. Based on clinical trial data, published literature and expert input, we have developed a decision-analytic model, composed of a decision-tree and a semi-Markov module, to evaluate the health economic properties of treatment with patiromer, for European countries.