Dr. High Yield Psychiatry Practice Test 2026 - Free Psychiatry Practice Questions and Study Guide

Vomiting in purging-type anorexia nervosa causes loss of stomach acid (hydrochloric acid). Losing HCl means both hydrogen ions and chloride are depleted, producing hypochloremia. The body and kidneys respond by retaining bicarbonate to maintain balance, so serum bicarbonate rises, resulting in metabolic alkalosis. This combination—low chloride with high bicarbonate—is the classic electrolyte pattern seen with purging behaviors. Potassium is often low as well due to GI losses and renal excretion, but the defining pair described here is low chloride with high bicarbonate. The other patterns don’t fit the gastric-alkalosis picture produced by recurrent vomiting.