Functional disorders of the gastrointestinal tract are those in which the bowel looks normal but does not work as it is designed to work. The most commonly found symptoms from those who suffer from these disorders are constipation and irritable bowel syndrome (IBS).

Functional disorders are caused primarily by eating a diet that is too low in fiber, by not drinking enough water or other fluids, by not getting enough daily exercise, by traveling or other changes in daily routine that disrupts digestion, by eating large amounts of milk and milk products, by being overly stressed, by resisting the urge to have bowel movements, by overusing laxatives, by taking antacid medications on a regular basis, and certain medications such as antidepressants, strong pain relievers, or iron pills, and also conditions such as pregnancy.