Author: Dylan Luyten, MD Educational Pearls:   Most important questions to answer with low potassium are 1. What are their symptoms? 2. Can they take potassium by mouth? Oral repletion is faster, cheaper, and more effective than IV repletion. Give IV potassium when patients have K < 2.5 mmol/L or present with arrhythmias and/or characteristic EKG changes (flattened T waves). Most patients who are hypokalemic are hypomagnesemic and require magnesium supplementation.  Checking a level is unnecessary.   References Ashurst J, Sergent SR, Wagner BJ, Kim J. Evidence-based management of potassium disorders in the emergency department. Emerg Med Pract. 2016 Nov 22;18(Suppl Points & Pearls):S1-S2   Whang R, Flink EB, Dyckner T, et al. Magnesium depletion as a cause of refractory potassium repletion. Arch Intern Med 1985; 145:1686.