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Fybogel (ispaghula husk)

On this page

  1. About Fybogel
  2. Key facts
  3. Who can and cannot take Fybogel
  4. How and when to take it
  5. Side effects
  6. Pregnancy and breastfeeding
  7. Cautions with other medicines
  8. Common questions about Fybogel

1. About Fybogel

Fybogel is a laxative taken to treat constipation (difficulty pooing).

It comes as plain or fruit-flavoured granules that you mix with water to make a high-fibre drink.

Fybogel is available on prescription and to buy from pharmacies and supermarkets.

2. Key facts

  • Fybogel is a high-fibre drink that you take in the morning and evening, preferably after a meal.
  • Fybogel takes 2 or 3 days to work.
  • When taking this type of laxative, make sure you drink plenty of fluids.
  • The main side effects are wind and bloating.
  • Fybogel is also called ispaghula husk and Ispage.

3. Who can and cannot take Fybogel

Fybogel can be taken by adults including pregnant and breastfeeding women.

Fybogel can be taken by children aged 6 years and older. Do not give Fybogel to a child under 6 years unless your doctor has said it's OK.

Fybogel is not suitable for everyone. To make sure Fybogel is safe for you, tell your doctor or pharmacist if you have:

  • had an allergic reaction to Fybogel or any other medicines in the past
  • a bowel obstruction
  • muscle weakness of the bowel (colonic atony)
  • a rare genetic illness called phenylketonuria

4. How and when to take it

Fybogel comes as sachets of plain, orange or lemon-flavoured granules.

It's best to take Fybogel after a meal or snack.


The usual dose for constipation in:

  • adults and children aged 13 years and over is 1 sachet of Fybogel granules twice a day
  • children aged 6 to 12 years is ½ to 1 level 5ml spoonful of Fybogel granules twice a day
  • children under the age of 6 years (only under medical supervision) is ½ to 1 level 5ml spoonful of Fybogel granules twice a day

How to take it

To make up the medicine, open the sachet and empty the granules into a glass. Add at least 150mls (¼ pint) of cold water to the glass.

Stir well until all the granules have dissolved and the Fybogel solution is clear or slightly hazy, and then drink it straight away.

Try not to breathe in the powder when you make up the Fybogel drink, as it can occasionally trigger a mild allergic reaction.

Have your evening drink of Fybogel at least an hour before going to bed. Drinking Fybogel just before you go to sleep increases the chances of it causing a blockage in the gut.

Aim to drink 6 to 8 glasses of fluid during the day while you're taking Fybogel or the constipation may get worse.

What if I forget to take it?

If you forget a dose of Fybogel, do not worry. Just take the next dose at the usual time.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

What if I take too much?

Taking too much Fybogel is unlikely to harm you. If this happens, drink plenty of water.

If you're worried, talk to your doctor or pharmacist for advice.

5. Side effects

Like all medicines, Fybogel may cause side effects in some people, but many people have no side effects or only minor ones.

Common side effects

The most common side effects, which happen in more than 1 in 100 people, are wind and bloating.

This sometimes happens because of the sudden increase of fibre in your diet.

It should get better after a few days. If the side effects carry on, or if you're worried, talk to your doctor or pharmacist.

Mild allergic reaction

It's possible to have a mild allergic reaction such as itchy eyes, nose or skin.

You're more likely to have a mild allergic reaction to Fybogel if you have had an allergic reaction before and if you're exposed to the powder regularly (for example, if you're a carer).

If you think you're having a mild allergic reaction to Fybogel, stop taking it and ask your pharmacist or doctor for advice.

Serious side effects

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to Fybogel.

Immediate action required: Call 999 or go to A&E now if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of Fybogel. For a full list, see the leaflet inside your medicines packet.


You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

6. Pregnancy and breastfeeding

Fybogel is generally safe to take during pregnancy and while breastfeeding.


For safety, tell your pharmacist or doctor if you're trying to get pregnant, already pregnant, or you're breastfeeding.

For more information about how laxatives can affect you and your baby during pregnancy, read this leaflet on the Best Use of Medicines in Pregnancy (BUMPS) website.

7. Cautions with other medicines

Fybogel can change the way some medicines work.

Tell your doctor if you are taking these medicines before starting Fybogel:

There's some evidence that Fybogel stops iron being taken in properly by the body.

If you need iron supplements, it's best to take them at least 1 hour before, or 4 hours after, you take Fybogel.

Mixing Fybogel with herbal remedies and supplements

There are no known problems with taking herbal remedies and supplements with Fybogel.

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

8. Common questions about Fybogel

How does Fybogel work?

Fybogel is called a bulk laxative. It helps to bulk up poo with fluid so it's softer and easier to pass.

When will I feel better?

It takes 2 to 3 days for Fybogel to work.

Talk to your doctor if you're still constipated after 3 days.

How long will I take Fybogel for?

You can take Fybogel for as long as the constipation lasts, or for as long as your doctor has recommended.

This will usually be for up to a week.

For more serious constipation, and if you're taking Fybogel to increase the fibre in your diet, your doctor may recommend that you take it for many months.

Is it safe to take Fybogel for a long time?

Ideally, you should only use Fybogel occasionally and for a few days at a time.

Using laxatives like Fybogel for longer can lead to prolonged diarrhoea.

It can also cause an electrolyte imbalance. This is 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 spasm and twitching and even convulsions.

But there are some situations where you may need to take Fybogel for many months – for instance, if you need to increase the fibre in your diet.

Your doctor will decide exactly how long and how much Fybogel you need to take.

Can I take different laxatives together?

For most people, 1 laxative will be enough to relieve constipation.

Occasionally, you may need to take 2 different types of laxatives at the same time to get your bowels moving again.

Only take 2 laxatives together on the advice of your doctor or pharmacist, as there's an increased risk of side effects.

Are other laxatives any better?

There are other types of laxatives. They work in a different way from Fybogel, but are equally good at treating constipation.

Some may work more quickly than Fybogel.

  • Osmotic laxatives (for example, lactulose). These draw water from the rest of the body into your bowel to soften poo and make it easier to pass. They take 2 or 3 days to work.
  • Stimulant laxatives (for example, senna and bisacodyl). These speed up your bowels by stimulating the nerves that control the muscles lining your gut. They work more quickly than other laxatives. If you take them at bedtime, they work overnight.
  • Surface-wetting laxatives (for example, arachis oil and docusate sodium). These allow water to get into poo to soften it and make it easier to pass.
Can I take it with IBS remedies?

You can take Fybogel alongside IBS remedies such as Buscopan.

Can I take Fybogel after an operation?

Yes, you can take Fybogel to relieve constipation after surgery.

Will it affect my fertility?

There's no firm evidence to suggest that taking Fybogel will reduce fertility in either men or women.

Will it affect my contraception?

Fybogel does not affect any type of contraception, including the contraceptive pill or emergency contraception, unless you have severe diarrhoea (6 to 8 watery poos in 24 hours) for more than 24 hours.

If you have severe diarrhoea, your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.

Read more about what to do if you're on the pill and you're vomiting or have diarrhoea.

Is there any food or drink I need to avoid?

You can eat and drink normally while taking Fybogel.

It might help to stop eating pastries, puddings, sweets, cheese and cake for a while, as these foods can make constipation worse.

Can I drink alcohol with it?

Yes, you can drink alcohol with Fybogel.

Can lifestyle changes help constipation?

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

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

  • get more fibre in to your diet – aim for about 30g of fibre a day. High-fibre foods include fruit, vegetables and cereals. If you're 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