Common questions about senna

Senna is a type of laxative called a stimulant laxative. It stimulates the muscles that line your gut, helping them to move poo along your bowel.

Senna takes about 8 hours to work.

Talk to your doctor if you are still constipated after 3 days. They may be able to suggest a different medicine.

Ideally, you'll only take senna occasionally and for a few days at a time.

Taking senna for longer can lead to diarrhoea. Stop taking it if you get diarrhoea.

It can also cause an electrolyte imbalance, where levels of substances like sodium, potassium and magnesium in your body get too high or too low. A severe electrolyte imbalance can cause serious health problems such as:

• muscle spasms
• twitching
• you having a seizure or fit

Using senna for many weeks, even months, could also stop your bowel working properly on its own.

There are other types of laxatives. They work in a different way to senna but are equally good at treating constipation. Some take longer to work than senna but are more gentle and should be tried first.

Bulk-forming laxatives, for example Fybogel and methylcellulose, increase the "bulk" or weight of poo which in turn stimulates your bowel. These laxatives take 2 or 3 days to work.

Osmotic laxatives, for example lactulose, draw water from the rest of the body into your bowel to soften poo and make it easier to pass. They take at least 2 days to work.

Surface-wetting laxatives, for example docusate, let water into poo to soften it and make it easier to pass.

Only use senna if you have tried these other types of laxatives first.

It's quite common to have constipation after surgery. Using a laxative may help relieve the discomfort.

If you have constipation after an operation, it's better to use lactulose because it's gentler on your stomach muscles than senna.

Senna does not affect any type of contraception, including the combined pill and emergency contraception, unless you have severe diarrhoea for more than 24 hours.

But if senna is not working for you and you have severe diarrhoea, your contraceptive pills may not protect you from pregnancy. Check the pill packet to find out what to do.

Find out more:

• what to do if you have diarrhoea when taking the combined pill
• what to do if you have diarrhoea when taking the progestogen-only pill

Taking senna should not affect your ability to drive or ride a bike.

Yes, you can drink alcohol with senna.

You can eat and drink normally with senna.

It might help to eat less of foods such as pastries, puddings, sweets, cheese and cake for a while, as these foods can make constipation worse.

It's often possible to relieve constipation without having to use laxatives.

Before trying senna, or to stop constipation coming back, it may help to:

• get more fibre into your diet – aim for about 30g of fibre a day. High-fibre foods include fruit, vegetables and cereals. If you are not used to a high-fibre diet, it may be best to increase the amount of fibre you eat gradually
• add bulking agents, such as wheat bran, to your diet. These will help make your poo softer and easier to pass (although bran and fibre can sometimes make bloating worse)
• drink plenty of water – to keep poo soft
• exercise – keeping your body active will help to keep your gut moving

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