An osmotic laxative for constipation
Macrogol
An osmotic laxative that draws water into the bowel to soften stool and relieve constipation.
What is Macrogol?
Macrogol (Movicol, Laxido) is an osmotic laxative made of polyethylene glycol mixed into a drink. It draws water into the bowel, softening the stool and making it easier to pass. It is a first-choice laxative in the UK for ongoing constipation and is gentle enough for regular use.
Education and reference only. This is a plain-language guide to Macrogol — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Macrogol is an osmotic laxative used to treat constipation, including the harder type and constipation that has lasted a long time. It comes as a powder dissolved in water to make a drink, available on prescription and to buy from pharmacies. In the UK it is often a first choice and can be used regularly, including in children under advice.
How it works
Macrogol holds water in the bowel by an osmotic effect, so the stool becomes softer and bulkier and is easier and more comfortable to pass. Unlike stimulant laxatives, it does not directly make the bowel muscle contract; it works by changing the water content of the stool. This makes it well suited to softening hard stools and to longer-term use.
Company & origin
Originated / developed by: Various manufacturers.
A widely used osmotic laxative (polyethylene glycol) recommended in UK constipation guidance.
Practical use
How to take Macrogol
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Dissolve each sachet in water as directed and drink the whole amount.
- It can be used regularly for ongoing constipation, as advised by your clinician or pharmacist.
- Allow a day or two for the full effect, and keep drinking fluids during the day.
- If used to clear a build-up of hard stool, follow the specific instructions given to you.
- If you miss a dose, take the next one as planned — there is no need to double up.
Weighing it up
Advantages & disadvantages of Macrogol
Advantages
- Gently softens hard stools and is suitable for regular, longer-term use.
- A first-choice laxative in UK guidance and usable in children under advice.
- Adds fluid to the bowel, so it is less likely to cause cramping than stimulant laxatives.
Disadvantages
- Works more slowly than stimulant laxatives, so it is not ideal for fast relief.
- Needs to be mixed with water, and the volume can be off-putting for some people.
- Can cause bloating, wind or mild tummy discomfort.
Practical use
Good to know
Because each sachet is mixed with water, macrogol also helps keep you hydrated, which supports its effect. It can take a day or more to work fully, so it is not the fastest option for sudden constipation. It is generally gentle and suitable for ongoing use, and higher amounts under medical advice can be used to clear a blockage of hard stool (faecal impaction). Keep drinking enough fluids generally while using it.
Who should not take it / use with caution
- People with a suspected or known bowel obstruction or perforation.
- People with severe inflammatory bowel disease, such as a severe ulcerative colitis flare, unless a clinician advises.
- Anyone who has reacted to it before; check higher-dose use carefully if you have heart or kidney problems.
Monitoring
- Whether stools become softer and constipation eases.
- Bloating, wind or, if too much is taken, loose stools.
- Fluid intake, and body salts if high doses are used in vulnerable people.
Side effects
- Bloating, wind and tummy rumbling.
- Mild tummy discomfort or, if too much is taken, loose stools.
- Rarely, nausea or, with large doses, changes in body salts in people with certain conditions.
Key interactions
- It can briefly affect how well other medicines are absorbed, so spacing doses can help.
- Few significant drug interactions; large doses to clear impaction need care with heart and kidney conditions.
- Tell your pharmacist about your other medicines before regular use.
Available as: Powder sachets dissolved in water to make an oral drink.
Answers
Macrogol: frequently asked questions
How long does macrogol take to work?
It usually takes a day or two to work fully, because it softens the stool gradually rather than forcing the bowel to contract.
Can I take macrogol long term?
Yes, macrogol is generally gentle and can be used regularly for ongoing constipation, often under the guidance of a clinician.
What is the difference between macrogol and senna?
Macrogol is an osmotic laxative that draws water in to soften stool, while senna is a stimulant laxative that makes the bowel muscle contract. Macrogol tends to cause less cramping.
Does it matter how much water I use?
Yes — dissolve each sachet in the amount of water on the instructions, as this is part of how it works. Drinking enough fluid generally also helps.
Can children take macrogol?
Yes, macrogol is commonly used for constipation in children, but always follow the specific instructions and advice from your clinician or pharmacist.
The wider class
About Laxatives
Macrogol belongs to the laxatives class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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