Constipation is one of the most common gastrointestinal complaints in the United States and can seriously affect quality of life. It is an acute or chronic condition in which bowel movements are infrequent and difficult to eliminate. In severe cases, constipation may cause bowel obstruction. Constipation is a symptom, rather than a disease, resulting from a number of causes and disorders, including dietary factors, neurologic disorders, psychiatric disorders, colon disease, metabolic abnormalities, and medication side effects. This may explain the high prevalence rates and associated excessive costs. This article assists the provider in identifying the correct diagnoses associated with constipation and guiding the practitioner through obtaining a pertinent medical history, performing a comprehensive physical examination, and prescribing the appropriate diagnostics tests. A diagnostic algorithm that considers an extensive list of differential diagnoses including medications contributing to constipation is provided to assist the practitioner in evaluating and diagnosing the cause(s) of the constipation.