Expert reviewer, Alastair Bovell, Lead Clinical Pharmacist Bupa UK.
Next review due: March 2020

Laxatives are foods or medicines that help you empty your bowels. You can use them to treat constipation or to clear your bowels before a medical procedure.

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How do laxatives work?

There are several types of laxative – you can buy some of them without a prescription. Each type of laxative works in a different way to help relieve or prevent constipation.

Bulk-forming laxatives

These are also known as fibre supplements, and include wheat or oat bran, ispaghula husk, methylcellulose and sterculia. They work in a similar way to fibre – they absorb water while in your bowel and increase the bulk of your stools (faeces). This helps make your stools softer, and encourages your bowels to push the stools out.

Your doctor or pharmacist may recommend bulk-forming laxatives if you’re slightly constipated and you’re finding it difficult to get more natural fibre in your diet. Your doctor may also prescribe a bulk-forming laxative if you have a colostomy or ileostomy bag, piles (haemorrhoids) or chronic diarrhoea.

Bulk-forming laxatives usually start working in 24 hours, but may take two to three days to work fully.

Osmotic laxatives

These laxatives work by increasing the amount of water in your stools, which makes them easier to pass. They include lactulose, macrogols, sodium citrate enema and phosphate enema.

If a bulk-forming laxative doesn’t work and your stools are still hard, you may need an osmotic laxative. Osmotic laxatives may take one to two days to start working.

Stimulant laxatives

This type of laxative works by stimulating nerves in your bowel, thus encouraging your bowel muscles to move and push your stools out. Stimulant laxatives include senna and glycerol or bisacodyl.

If your stools are soft but they’re still too difficult to pass, your doctor may suggest trying a stimulant laxative. Stimulant laxatives come in different forms. Tablets, capsules and liquids start to have an effect within six to 12 hours. Your doctor or pharmacist may advise you take them at night, so that they work by the next morning. Suppositories (solid, bullet-shaped preparations you put inside your back passage) work within 15 to 60 minutes.

Faecal softener laxatives

The main type of faecal softener is docusate. It works by lubricating and softening your stools. This makes them easier to pass.

Lubricant laxatives

These include arachis oil and liquid paraffin. They work by lubricating your intestine, easing the passage of the stool. These laxatives come as tablets and enemas (liquid injected through a thin tube into your back passage). They don’t always work well on their own. Your doctor may prescribe these with another laxative.

Why do I need to take laxatives?

Your GP or pharmacist may recommend you take laxatives if you have constipation. But you should only take laxatives for constipation if changing your diet and lifestyle hasn’t helped your symptoms.

If you’re constipated, it means you’re having trouble emptying your bowels. This can mean different things to different people, because bowel habits vary from person to person. But you may be constipated if you have any of the following problems.

  • You have a bowel movement less often than three times a week.
  • You need to strain to open your bowels.
  • Your stools (faeces) are harder than usual.

Your doctor may recommend you take laxatives if straining could make an existing medical condition worse, such as angina or piles (haemorrhoids). You may also need to take laxatives if you regularly take medicines that could make you constipated, such as some antidepressants and opioid painkillers.

Laxatives may be prescribed to clear your bowels before surgery. You’ll also need to take them if you’re having a test to look inside your large bowel, such as a barium enema or colonoscopy.

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How to take laxatives

Laxatives are available in many different forms. Your doctor or pharmacist will recommend a type that suits your needs, lifestyle and symptoms.

You can take laxatives as:

  • tablets, syrups or capsules that you swallow
  • powders or granules that you mix in water and drink
  • suppositories (solid, bullet-shaped preparations that you put inside your back passage)
  • enemas (liquid injected through a thin tube into your back passage)

If you’re taking tablets, your doctor or pharmacist may advise taking them at night, as they take longer to work than suppositories and enemas. This means you’ll be able to pass a stool in the morning.

Bulk-forming laxatives usually come as powders or granules. It's important to drink lots of water when you take them to stop your bowel getting blocked up. You’ll also need to drink plenty of fluids while taking osmotic laxatives to make sure you don’t get dehydrated. Make sure you check what’s recommended for your medicine.

How long should I take laxatives for?

You should take laxatives for the shortest length of time possible to ease your constipation. Taking some types, such as stimulant laxatives, for a long time can be harmful. You will usually be advised to stop taking laxatives once your stools are soft and easy to pass again.

Sometimes, you may need to take laxatives for weeks or months, especially if you have chronic constipation.

Always read the patient information leaflet that comes with your medicine. If you have any questions, ask your pharmacist or doctor for advice

Can everyone take laxatives?

Laxatives aren’t always suitable for everyone.

Check with your GP or pharmacist before taking a laxative if:

  • you’re pregnant or breastfeeding
  • you know that your kidneys or liver aren't working properly
  • you have an inflammatory bowel disease such as ulcerative colitis

You shouldn't give laxatives to children unless your doctor has prescribed them.

Side-effects of laxatives

Laxatives have many possible side-effects – there’s too many to list them all here. But below are some of the most common ones.

  • Bulk-forming laxatives can make you bloated and cause wind, stomach pains and cramps. Rarely, they can block your bowel.
  • Osmotic laxatives can cause bloating, wind, nausea (feeling sick) and stomach cramps. You may be able to reduce any nausea by taking osmotic laxatives with water, fruit juice or food. You may become dehydrated if you don’t drink the recommended amount of fluid.
  • Stimulant laxatives can cause stomach pains and cramping. They may give you diarrhoea if you use them too regularly.
  • Suppositories can irritate the skin around your anus (back passage).

Most side-effects can be avoided or reduced if you increase the dose of laxative tablets, syrups or capsules gradually. Start at the lowest dose and, if necessary, increase the dose every few days.

Some laxatives can stop your digestive system from absorbing certain nutrients and some other medicines you’re taking. This is why you should take laxatives for the shortest length of time possible. Check with your GP or pharmacist before you take any other medicines, vitamin supplements or herbal remedies at the same time as a laxative.

Please read the patient information leaflet that comes with your medicine for more information.

Frequently asked questions

  • No, laxatives can’t help you lose weight. In fact, taking laxatives if you don’t need them, or taking them regularly, can be harmful. The best way to lose weight is by eating a healthy diet and exercising regularly.

    Laxatives help you empty your bowels. But they won’t stop you absorbing calories. Laxatives work on your lower bowel after most of the calories in your food have already been absorbed.

    Taking laxatives occasionally for constipation shouldn’t do you any harm. But taking them regularly may make you dehydrated if you don’t drink the recommended amount of fluid. Dehydration can make you feel weak and faint and cause headaches. If you take too many laxatives, this may cause diarrhoea or block your bowel. Taking laxatives regularly may also affect the electrolyte and mineral balance in your body. This can cause muscle aches and pains and make your heart race (palpitations).

  • If you’re having fewer bowel movements than normal, or you’re having to strain, then you may be constipated. If you’re constipated, it may help if you eat more fibre and drink more fluid. Try eating more fruit and vegetables and cereals containing bran. Aim for around 30g of natural fibre a day. Too much fibre can cause wind and bloating though, so you’ll need to get the balance right and see what works for you. Exercising regularly may also help to ease your symptoms.

    If changing your lifestyle doesn’t work, then you could try laxatives. But speak to your doctor or pharmacist first. They may recommend you try a bulk-forming laxative to start with. This will help you increase the amount of fibre in your diet.

    Several other types of laxative are available over the counter from pharmacies and also on prescription. Some may be more effective for you than others, depending on your symptoms and circumstances. Ask your GP or pharmacist for advice.

  • Foods that are high in fibre can act as natural laxatives by making your stools softer and easier to pass. A food is high in fibre if it contains at least 6g of fibre in every 100g. In the UK, adults are recommended to eat 30g of fibre every day. Foods that are high in sorbitol can also help to prevent and treat constipation.

    Natural laxatives include many fruits, vegetables, beans, pulses, nuts and seeds. Fruits that can act as laxatives include apricots, grapes, plums and prunes. You could combine these with oats, oat bran and water to make a breakfast porridge, for example. Research has found that prunes work well as a natural laxative and are as effective as bulk-forming laxatives containing ispaghula husk in treating constipation.

    If you add more fibre into your diet, you’ll also need to drink more fluid, as this will help the fibre to work properly. Aim for eight to ten cups of fluid each day. If you don’t drink enough fluid, you could become dehydrated.

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Related information

    • Laxatives, stool softeners and prokinetic agents. Medscape., updated April 2016
    • Constipation. BMJ Best Practice., last updated January 2016
    • Laxatives. NICE British National Formulary., reviewed February 2017
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    • Constipation. NICE Clinical Knowledge Summaries., last revised October 2015
    • Eating disorders. NICE Clinical Knowledge Summaries., last revised October 2014
    • Laxative abuse – Beat’s call to action., published 23 February 2015
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  • Reviewed by Pippa Coulter, Specialist Health Editor, Bupa Health Content team, March 2017
    Expert reviewer, Alastair Bovell, Lead Clinical Pharmacist Bupa UK.
    Next review due: March 2020

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