Amino acid formulations useful for treating diarrhea in a subject in need thereof are described herein. Such amino acid formulations and methods comprising administering same to a subject are useful for treating diarrhea, particularly diarrhea caused by or associated with bacterial infections wherein secretagogue-stimulated anion secretion from the intestinal crypt contributes to at least one symptom of diarrhea in the subject. Use of these amino acid formulations for the treatment of diarrhea in general or diarrhea associated with secretagogue-stimulated anion secretion from the intestinal crypt are encompassed herein, as are their use in the preparation of a medicament for the treatment of diarrhea in general or diarrhea associated with secretagogue- stimulated anion secretion from the intestinal crypt.