Hyperkalemia is a medical condition that requires immediate recognition and treatment to prevent the development of life-threatening arrhythmias. Pseudohyperkalemia is most commonly due to specimen haemolysis and is often recognised by laboratory scientists who subsequently report test results with cautionary warnings. The authors present a case of pseudohyperkalemia in a patient with chronic lymphocytic leukaemia that was the result of white blood cell lysis during phlebotomy. False elevations of potassium from this condition may not be reported with a warning from the laboratory. This places the patient at risk of unnecessary and potentially dangerous treatments. This phenomenon has not been published in the emergency medicine literature to date.