This review article describes the pathophysiology and common aetiologies of hyperkalaemia including pseudohyperkalaemia, renal impairment, medication, rhabdomyolysis and aldosterone deficiency. Two clinical cases are used to describe symptoms (mainly muscle weakness and arrhythmias) and illustrate different management options. An approach to management including relevant investigations and interpretation of ECG changes is described. Emergency drug treatments are outlined and the effectiveness of individual therapeutic methods in reducing the potassium concentration described. Chronic management is mentioned but is outside the scope of this article. Hyperkalaemia is a rare but potentially life threatening emergency. It is a manifestation of a disease and therefore the incidence in children is not known. Quick and effective intervention may be necessary and clinicians must be adept at managing this condition. This overview provides two clinical scenarios and summarises aetiologies, investigations and management.