DOI: 10.1373/clinchem.2009.127506


A 64-year-old woman with a history of paranoid schizophrenia, hypertension, hyperlipidemia, and unexplained chronic hypokalemia presented in the outpatient psychiatric clinic for a routine follow-up visit with no specific complaints. Her history and review of systems revealed no remarkable findings. Her medications included an over-the-counter oral potassium supplement (equivalent to 2.5 mmol 3 times daily) and olanzapine (10 mg daily). She appeared well, and her physical exam was notable only for hypertension (188/105 mm Hg). A blood sample was obtained and blood chemistry tests were performed for routine monitoring.