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About senna

Senna is a natural laxative made from the leaves and fruit of the senna plant. It's used to treat difficulty pooing (constipation). It works by stimulating the muscles in your gut.

Before trying senna, it's better to try other ways to help your constipation by:

  • having more fibre in your diet
  • drinking more water and exercising

Only use senna if you have tried other types of laxatives first such as:

  • bulk-forming laxatives like Fybogel (ispaghula husk) or methylcellulose
  • osmotic laxatives like lactulose or polyethylene glycol

Senna comes as tablets and as a liquid that you swallow (syrup).

It's available on prescription and to buy from pharmacies. You can buy small packs from supermarkets (up to 20 standard strength tablets, 10 maximum strength tablets or 100ml of syrup).

It's also combined with other ingredients in constipation remedies such as Manevac and Senokot Dual Relief tablets.

Key facts

  • Senna takes about 8 hours to work.
  • It's best to take it at bedtime so it works overnight.
  • The most common side effects are stomach cramps and diarrhoea. These are usually mild and do not last long.
  • Do not take senna for more than 1 week unless it has been prescribed for you. Long-term use of senna can stop your bowel working properly on its own.
  • Your pee may turn a red-brown colour while you take senna. This is harmless and returns to normal after you stop taking it.

Page last reviewed: 1 February 2022
Next review due: 1 February 2025