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Senna is a plant-based stimulant laxative for constipation.
What should I know about Senna?
It takes about 8 to 12 hours to work, so it is usually taken at bedtime. Try fibre, water and exercise first. Do not take it for more than 1 week unless a clinician advises it, as long-term use can affect the bowel.
What are the side effects?
Stomach cramps and diarrhoea are common. Urine may turn red-brown, which is harmless.
Who should check first?
Ask your pharmacist if you have a medical condition, or before giving it to a child.
When should I get help?
See a doctor if constipation has not improved after 3 days or gets worse. Read our constipation guide for warning signs.
Doses vary, so follow your prescriber, pharmacist and the medicine label. In Australia, call 000 in an emergency. Outside Australia, use your local emergency number.
Source: NHS: About senna. General education does not replace individual medical advice. Updated November 2026.
Explore our health guides and medicine FAQs. Medicine availability and product instructions vary by country; follow the leaflet supplied with your medicine.