Serum electrolytes as markers of vomiting in bulimia nervosa

Objective: Patients with bulimia nervosa often have serum electrolyte abnormalities that result from vomiting and/or laxative or diuretic use. Thus, serum electrolytes could serve as an objective marker of such behaviors. Method: This study is a retrospective examination of serum electrolyte levels and vomiting behavior in 138 bulimic women, and of serum electrolyte levels in 70 control women. Results: Logistic regression analyses demonstrated that only potassium values distinguished bulimic subjects from controls. Potassium levels below the lower limit of normal (3.7 mg/l) occurred only in the bulimic group. Discussion: Abnormally low values for potassium are a specific, but not sensitive, predictor of recent vomiting episodes.