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How do I relieve constipation on Mounjaro or Wegovy?

GLP Guidebook teamUpdated 21 Oct 202614 sourcesWritten from published sources
What we checked14 sources, each one opened and linked to the sentence it supportsLast checked 21 Oct 2026 · Next review due 21 Oct 2027 · How we write
The short answer

For constipation on Mounjaro (tirzepatide) or Wegovy (semaglutide), the NHS advises more fluids, fibre added gradually and a daily walk first. If that isn't helping, a pharmacist can suggest a laxative, usually a bulk-forming one first. The UK labels list constipation as very common; on Wegovy 2.4 mg it affected 24% vs 11% on placebo.

Before you go further
  • Side-effect rates come from each medicine’s UK label on emc, named each time.
  • Laxatives are named by their generic names only. We don’t rank products.

How common is constipation on Mounjaro and Wegovy?

Both UK leaflets list constipation as very common (more than 1 in 10 people) in weight-loss use.1,4

The Mounjaro (tirzepatide) leaflet says it is common (up to 1 in 10) in people treated for type 2 diabetes.1 The UK label gives no constipation percentage for the weight trials.2

On Wegovy (semaglutide) 2.4 mg, 24.2% had constipation over 68 weeks, against 11.1% on placebo (a dummy injection). On 7.2 mg it was 20.4% against 7.6%. The label calls it mild to moderate, but longer-lasting than other stomach effects.3 In the semaglutide trials, a typical bout lasted 47 days, against 35 on placebo.5

The NHS says it’s likely to be constipation if you’ve pooed fewer than 3 times in the last week. Dry, hard or lumpy poo and straining are other signs.6 Other side effects are in Guide 5: side effects and risks.

What does the NHS say helps?

The NHS says to drink plenty of fluids, add fibre gradually and take a daily walk or run. You may notice a difference within a few days.6

It suggests sorbitol fruits, such as apples, apricots, grapes, raisins, raspberries and strawberries, plus wheat bran, oats or linseed. It also says to avoid alcohol and to rest your feet on a low stool on the toilet. It can take a few weeks.6

UK guidelines say adults should get 30 g of fibre a day; most eat about 20 g.7 A small US trial, not a GLP‑1 study, gave 2 kiwifruit or 100 g of prunes a day to adults with long-term constipation. Both eased straining over 4 weeks.8

Which laxative, and for how long?

Without a prescription, the NHS says a bulk-forming laxative is usually best to try first, and a pharmacist can help you choose.9

Bulk-forming ones such as ispaghula husk take up to 3 days to work. Osmotic ones such as macrogol take 2 to 3 days, and stimulants such as senna 6 to 12 hours. Drink plenty of fluids with bulk-forming or osmotic ones.9

With a laxative you bought, stop once you’re better and don’t take it for more than 7 days. If 3 days haven’t helped, speak to a doctor or pharmacist. Used too often or for too long, laxatives can cause dehydration, low potassium or a blocked bowel.9

If a medicine causes your constipation, the NHS says to see a GP, and to speak to them before stopping it.6 For significant stomach symptoms, the UK Wegovy label tells prescribers to consider delaying the next dose increase or going back a dose.3

When is constipation on a GLP‑1 serious?

The UK Wegovy leaflet lists bowel obstruction, which it describes as a severe form of constipation with stomach ache, bloating or vomiting.4

Its frequency isn’t known; the cases were reported after it went on sale.3,4 The UK Mounjaro leaflet lists slower stomach emptying as uncommon, but not bowel obstruction.1

The NHS says long-term constipation can lead to faecal impaction, where poo builds up in the rectum. Its main symptom is diarrhoea leaking around the hard poo. Removing it is a job for a healthcare professional, not something to do yourself.6 For other emergencies, see When should I call 999 or 111 on a GLP‑1?

What do people on Mounjaro and Wegovy report about constipation?

From public patient forums: 10 Reddit threads in r/Zepbound, r/Wegovy, r/Semaglutide, r/Ozempic and r/MounjaroUK, read in October 2026. Personal reports, not medical evidence.

What people describe

  • Matches the label Several say it began in the first weeks or after a dose increase, and a few say months in. The UK Wegovy label says stomach side effects were most often reported during dose increases, and that constipation lasted longer. In the semaglutide trials it stayed above placebo for all 68 weeks.3,5
  • Matches the NHS Several describe poo so hard it got stuck, and a few needed emergency care for it. The NHS says long-term constipation can lead to faecal impaction.6
  • Matches the NHS A few had watery poo while still badly blocked. The NHS says leaking diarrhoea is the main symptom of faecal impaction.6
  • Matches the UK label Several say the anti-sickness medicine ondansetron made it worse. A UK ondansetron label lists constipation as a common side effect.11

Advice people share

  • Matches the NHS and a trial Most start with more water and fibre, added slowly, and many eat prunes or 2 kiwifruit a day. The NHS advises fluids, gradual fibre and sorbitol fruits. A small US trial, not of GLP‑1 users, found kiwifruit and prunes eased straining.6,8
  • Not studied Most replies in threads about blockages say not to let it run past a few days. We found no NHS rule on how many days is too long. The NHS does say to speak to a doctor or pharmacist if 3 days of laxatives haven’t helped.9
  • NHS says otherwise Some take stimulant laxatives such as senna every day for weeks. The NHS says not to take senna for more than 7 days unless a doctor or pharmacist has advised it.10
  • Label says otherwise A few skip or put off GLP‑1 doses on their own. The UK leaflets say not to stop without talking to your doctor. The Wegovy label leaves dose changes for stomach symptoms to the prescriber.1,3,4
Get help now: call 999 or go to A&E if you have a stomach ache and:12
  • it came on very suddenly or is severe
  • it hurts when you touch your stomach
  • you cannot poo or fart
  • your poo is bloody or black and sticky and extremely smelly
  • you have diabetes and you’re vomiting
  • you’re vomiting blood, or your vomit looks like ground coffee

The NHS says not to drive yourself to A&E.12

Ask for an urgent GP appointment or contact NHS 111 if a stomach ache gets much worse or keeps coming back. Do the same for a stomach ache with bloating that won’t go away, or with bleeding from your bottom.12 The NHS 111 page sends Northern Ireland readers to nidirect, which says to phone the GP out-of-hours service when your surgery is closed.13,14

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Related questions

When should I call 999 or 111 on a GLP-1? How do I report a side effect to the Yellow Card scheme? Why am I always cold on Mounjaro? Why am I not losing weight on Mounjaro or Wegovy?
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Sources

  1. Eli Lilly. Mounjaro KwikPen (tirzepatide) UK patient information leaflet, last revised Aug 2026, sections 3 and 4. UK label. medicines.org.uk (emc)
  2. Eli Lilly. Mounjaro KwikPen (tirzepatide) UK summary of product characteristics (SmPC), date of revision 29 Aug 2026, section 4.8. UK label. medicines.org.uk (emc)
  3. Novo Nordisk. Wegovy (semaglutide) UK SmPC, date of revision 09/2026, sections 4.2 and 4.8. UK label. medicines.org.uk (emc)
  4. Novo Nordisk. Wegovy (semaglutide) UK patient information leaflet, last revised 08/2026, sections 3 and 4. UK label. medicines.org.uk (emc)
  5. Wharton S et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg in adults with overweight or obesity, and the relationship between gastrointestinal adverse events and weight loss. Diabetes Obes Metab 2022;24(1):94-105. DOI 10.1111/dom.14551. PMID 34514682. Trials funded by Novo Nordisk. PubMed
  6. NHS. Constipation (page last reviewed 26 Oct 2023). nhs.uk
  7. NHS. How to get more fibre into your diet (page last reviewed 2 Mar 2026). nhs.uk
  8. Chey SW et al. Exploratory comparative effectiveness trial of green kiwifruit, psyllium, or prunes in US patients with chronic constipation. Am J Gastroenterol 2021;116(6):1304-12. DOI 10.14309/ajg.0000000000001149. PMID 34074830. 79 adults, 4 weeks; not a GLP-1 study. PubMed
  9. NHS. Laxatives (page last reviewed 30 Apr 2026). nhs.uk
  10. NHS. Senna (page last reviewed 24 Sep 2026). nhs.uk
  11. Ondansetron 4 mg film-coated tablets, UK SmPC, date of revision 31 Dec 2025, section 4.8. UK label. medicines.org.uk (emc)
  12. NHS. Stomach ache (page last reviewed 26 May 2023). nhs.uk
  13. NHS. When to use NHS 111 online or call 111 (page last reviewed 14 Nov 2022). nhs.uk
  14. nidirect (Northern Ireland). GP out of hours service. nidirect.gov.uk

Last checked 21 Oct 2026 · Next review due 21 Oct 2027 · Report an error

How this answer was made. Written by the GLP Guidebook team from the sources above. It's general information, not medical advice. The 'What people report' section summarises public patient forum posts we read; it is not medical evidence, and we never pass on advice that goes against the label. Talk to a qualified doctor before starting, stopping or changing any medicine. How we write