Fybogel (ispaghula husk)

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 can't 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.

How much to take

The normal 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 by accident 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 allergic reaction

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 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 to the UK safety scheme.

6. Pregnancy and breastfeeding

Fybogel is generally safe to take during pregnancy and while 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.


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

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:

  • carbamazepine (a medicine for epilepsy and mood problems)
  • digoxin (a heart medicine)
  • mesalazine (a medicine to treat gut problems)

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.


For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

8. Common questions

Page last reviewed: 24/01/2019
Next review due: 24/01/2022