H yperkalemia is common in hospitalized patients, with an estimated prevalence of 1%-10%. 1,2 Hyperkalemia can lead to life-threatening cardiac arrhythmias. The risk of arrhythmias increases with serum potassium values >6.5 mmol/L, and hyperkalemia is associated with increased in-hospital mortality. 3 Treatment for hyperkalemia is indicated by a combination of the absolute serum potassium level, the rate of change of potassium level, and the presence of electrocardiogram abnormalities.Intravenous insulin stimulates the sodium/potassium-ATP pump, leading to intracellular uptake of potassium. Recommendations vary regarding the optimal dosing of insulin and dextrose for the treatment of hyperkalemia. 4 Hypoglycemia is a common complication following treatment of hyperkalemia with insulin/dextrose. The reported incidence in hospitalized patients ranges from 6% to 75% depending on the population studied, the doses of insulin/ dextrose administered, and the definition of hypoglycemia. [5][6][7][8] Hypoglycemia itself is associated with increased morbidity and mortality in hospitalized patients. 9 The aims of this study were to describe the incidence of hypoglycemia following hyperkalemia treatment with intra-venous insulin/dextrose in inpatients in a large (900-bed) UK teaching hospital and to determine the risk factors predisposing to hypoglycemia.