Yes, Prozac causes low potassium. The body has 98% of its potassium in intracellular fluid and 2% in extracellular fluid. Potassium plays a critical role in many metabolic functions. The sodium-potassium ATPase pump regulates this balance by moving ions across the cell membrane against a concentration gradient. In order to enhance neuronal excitability, you can block potassium. Fluoxetine (Prozac) inhibits Kv1-mediated currents in various potassium channels.