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What Is Senna?

Senna is a plant-derived stimulant laxative used for short-term relief of occasional constipation. Its active compounds, called sennosides, are obtained from plants in the Senna genus and are available in over-the-counter tablets, liquids, and other oral preparations. Senna increases activity in the large intestine to help produce a bowel movement. It generally works within six to 12 hours, making bedtime administration common. Senna is also used under medical supervision in certain bowel-emptying regimens. It is intended for short-term use rather than routine treatment of persistent constipation without medical evaluation. Products vary in strength and age-specific dosing instructions.

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What Is Senna?

Senna is a plant-derived stimulant laxative used for short-term relief of occasional constipation. Its active compounds, called sennosides, are obtained from plants in the Senna genus and are available in over-the-counter tablets, liquids, and other oral preparations. Senna increases activity in the large intestine to help produce a bowel movement. It generally works within six to 12 hours, making bedtime administration common. Senna is also used under medical supervision in certain bowel-emptying regimens. It is intended for short-term use rather than routine treatment of persistent constipation without medical evaluation. Products vary in strength and age-specific dosing instructions.

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How Does Senna Work?

Senna contains sennosides, compounds that are converted by bacteria in the large intestine into active substances that stimulate bowel movement. These substances affect intestinal motility and promote the movement of water and electrolytes into the colon. The combined effects help soften stool and move intestinal contents toward the rectum. Senna acts primarily in the large intestine rather than immediately after swallowing. This explains why a bowel movement commonly occurs six to 12 hours after administration. Excessive stimulation can cause abdominal cramps and diarrhea. Senna does not correct the underlying cause of chronic constipation.

What Conditions Does Senna Treat?

Senna is used for temporary relief of occasional constipation, including infrequent or difficult bowel movements. Healthcare professionals may also include senna in selected bowel-emptying regimens before medical procedures. It is not intended to treat every cause of abdominal discomfort, bowel obstruction, or chronic constipation. Persistent constipation may be associated with medication effects, inadequate dietary fiber, dehydration, or an underlying medical condition. Patients with unexplained abdominal pain, nausea, vomiting, or a sudden change in bowel habits lasting more than two weeks should seek medical advice before using senna. Rectal bleeding requires medical assessment rather than additional laxative doses.

How Should Senna Be Taken?

Senna is taken orally, commonly at bedtime, according to the specific product label. For standard tablets containing 8.6 mg of sennosides, adults and children aged 12 years and older commonly start with two tablets once daily. Some labels permit increases to a maximum of four tablets twice daily, but maximum doses and pediatric directions vary by formulation. Children require age-appropriate dosing and supervision. A bowel movement generally occurs within six to 12 hours. Patients should take senna with adequate fluids and avoid exceeding the package directions. Laxative use beyond one week requires medical guidance. If constipation persists after treatment, the patient should seek evaluation rather than repeatedly increasing the dose.

What Are the Side Effects and Warnings of Senna?

Common adverse effects include abdominal cramps, stomach discomfort, nausea, and diarrhea. Senna may also cause harmless changes in urine color. Excessive doses or prolonged use can contribute to dehydration, electrolyte disturbances, and impaired normal bowel function. Patients should not use stimulant laxatives for more than one week unless directed by a healthcare professional. Those with unexplained abdominal pain, vomiting, suspected bowel obstruction, or a sudden persistent change in bowel habits need medical assessment before treatment. Stop taking senna and contact a clinician if rectal bleeding occurs or no bowel movement follows use. Severe diarrhea, weakness, or dizziness can indicate dehydration or electrolyte loss.

Common Questions About Senna

Is senna a stimulant laxative?

Yes. Senna contains sennosides that stimulate activity in the large intestine to relieve occasional constipation.

How long does senna take to work?

Senna generally produces a bowel movement within six to 12 hours. It is commonly taken at bedtime.

Can senna be used every day?

Senna should not be used for more than one week without medical direction. Persistent constipation requires evaluation rather than prolonged unsupervised laxative use.

Can senna cause stomach cramps?

Yes. Abdominal cramping and diarrhea are recognized adverse effects, particularly with higher doses.

References

DailyMed - SENNOSIDES tablet. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=829d24b7-a46a-4a29-88fe-180f35a2b6cd. Date Accessed November 6, 2026.

Senna. LiverTox. https://www.ncbi.nlm.nih.gov/books/NBK547922/. Date Accessed November 6, 2026.

Senna. MedlinePlus. https://medlineplus.gov/druginfo/meds/a601112.html. Date Accessed November 6, 2026.

Senna. National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/senna. Date Accessed November 6, 2026.

Sennosides. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Sennoside-A. Date Accessed November 6, 2026.