Most often, laxatives are prescribed to treat conditions related to constipation, a condition in which a person is unable to have regular bowel movements or is unable to do so comfortably. Several digestive conditions are related to constipation. For example, inflammatory bowel disease (which includes colitis and Crohn's disease) and encopresis both cause constipation that may be helped by the occasional use of mild laxatives. Research also shows that constipation resulting from the use of certain medications, such as opioid painkillers, may also be relieved by laxative use.

Short-term use of laxatives (except saline laxatives) may also be recommended for relief from constipation during pregnancy and shortly after giving birth and for constipation in patients confined to their beds. A physician may also suggest use of laxatives to clear the colon prior to having certain tests or procedures to examine part of or the entire intestine. Such procedures include a colonoscopy or  lower gastrointestinal (GI) series.

In addition to treating constipation, bulking agents (e.g., bran, psyllium) may be used to treat diarrhea.

Laxatives can also be helpful during periods when it is important to avoid straining during bowel movements, such as following surgery or when a person has certain medical conditions that can be worsened by straining. These include:

• Heart disease
• Hemorrhoids
• Hernia (rupture)
• High blood pressure (hypotension)
• History of stroke