Constipated on Mounjaro or Wegovy? Learn why weight loss injections cause constipation, the best foods, drinks and laxatives for relief, and when to seek help.
Do Mounjaro and Wegovy cause constipation?
Yes. Constipation is one of the most common side effects of both Mounjaro and Wegovy.
In the main clinical trials:
- Around 1 in 4 people taking Wegovy (semaglutide) reported constipation, compared with around 1 in 10 taking placebo
- Between around 1 in 9 and 1 in 6 people taking Mounjaro (tirzepatide), depending on the dose, reported constipation, compared with around 1 in 17 taking placebo
For most people, constipation is mild to moderate and can be managed with simple changes to diet, fluids and activity, sometimes with short-term help from a laxative.
This guide explains why it happens, what you can do about it, which laxatives are commonly used, and the warning signs that mean you should seek medical advice.
What counts as constipation?
Constipation does not just mean going to the toilet less often. You may be constipated if you:
- Open your bowels fewer than three times a week
- Pass stools that are hard, dry or lumpy
- Have to strain or find it painful
- Feel that you have not fully emptied your bowels
- Have bloating, stomach discomfort or cramps
It is also worth remembering that if you are eating much less, you will naturally produce less stool. Going slightly less often than before is not necessarily a problem, as long as stools are soft and easy to pass.
Why do weight loss injections cause constipation?
Several factors combine to slow things down.
1. Slower movement through the gut
Mounjaro and Wegovy slow the rate at which your stomach empties and can slow movement through the digestive system more generally.
When stool moves more slowly through the bowel, more water is absorbed from it, making it harder and drier.
2. Eating less food
Smaller portions mean less bulk passing through the bowel. Bulk is one of the signals that stimulates the bowel to move.
3. Eating less fibre
When appetite is low, fibre-rich foods such as vegetables, fruit and wholegrains are often the first to go, especially if people focus heavily on protein.
4. Drinking less
Many people drink less on weight loss injections, partly because they eat less, and partly because thirst is reduced. Dehydration makes stools harder.
5. Being less active
If you feel tired or nauseous in the early weeks, you may move less, and physical activity helps to keep the bowel working.
6. Other medicines
Some medicines can make constipation worse, including codeine and other opioid painkillers, iron tablets, some antidepressants and some blood pressure medicines.
How long does constipation last?
Constipation is most common in the first few weeks of treatment and after a dose increase.
For many people, it improves as the body adjusts.
For some, it can be a recurring issue for as long as they are on treatment, particularly at higher doses. If that applies to you, building long-term habits around fibre, fluids and activity is the key.
How to relieve constipation on Mounjaro or Wegovy
Start with these steps. Together, they resolve constipation for most people.
1. Drink more fluids
This is the simplest and most important step.
- Aim for around 6 to 8 glasses of fluid a day, and more in hot weather or when exercising
- Water, milk, herbal teas, and tea and coffee in moderation all count
- Sip throughout the day rather than drinking large amounts at once
- A warm drink in the morning can help stimulate the bowel
Fibre without fluid can make constipation worse, so always increase the two together.
2. Increase fibre gradually
UK guidance recommends that adults aim for 30g of fibre a day. Most people eat far less.
Good sources include:
- Oats and porridge
- Wholegrain or seeded bread, wholemeal pasta and brown rice
- Beans, lentils and chickpeas
- Vegetables, including the skins where edible
- Fruit, especially kiwi, pears, apples, berries, oranges and prunes
- Nuts and seeds, including chia seeds and ground flaxseed
Increase fibre slowly over a couple of weeks. A sudden jump can cause wind, bloating and cramps, especially while your digestion is already slowed.
3. Try foods with a natural laxative effect
Some foods are particularly helpful:
- Kiwi fruit: two a day has been shown in studies to improve bowel frequency
- Prunes and prune juice, which contain sorbitol
- Pears and apples
- Ground flaxseed or chia seeds stirred into yoghurt or porridge, with plenty of fluid
4. Keep moving
Physical activity stimulates the muscles of the bowel.
A daily walk, particularly after meals, can make a real difference. Any movement counts.
5. Build a toilet routine
- Do not ignore the urge to go. Delaying makes stools harder.
- Try sitting on the toilet at a regular time each day, such as after breakfast, when the bowel is naturally most active.
- Give yourself time and try not to rush.
- Raise your feet on a small footstool so your knees are higher than your hips. Lean forward with your elbows on your knees. This position helps the bowel to empty.
6. Eat regular meals
Skipping meals can slow the bowel further. Even small, regular meals help maintain a rhythm.
Our guide on what to eat on Mounjaro or Wegovy has more on building balanced meals with enough fibre and protein.
Can you take laxatives with Mounjaro or Wegovy?
Yes. Laxatives can generally be used alongside weight loss injections, and are often recommended for short-term relief when diet and fluid changes are not enough.
Speak to a pharmacist before starting one. They can recommend the most suitable type for you and check it is safe with your other medicines and health conditions.
There are four main types.
Bulk-forming laxatives
Example: ispaghula husk (such as Fybogel)
These work like dietary fibre, increasing the bulk of the stool and helping it hold water.
- Take two to three days to work
- Must be taken with plenty of fluid
- May cause bloating at first
- Best for mild constipation or prevention
Osmotic laxatives
Examples: macrogol (such as Laxido or Movicol), lactulose
These draw water into the bowel to soften the stool.
- Usually take one to three days to work
- Generally gentle and well tolerated
- Often the first choice recommended for constipation related to these medicines
Stimulant laxatives
Examples: senna, bisacodyl
These stimulate the muscles of the bowel to move.
- Usually work within 6 to 12 hours, so are often taken at bedtime
- Can cause cramping
- Intended for short-term use
Stool softeners
Example: docusate
These help water mix into the stool, making it softer and easier to pass.
Important points about laxatives
- Use the lowest effective dose for the shortest time needed
- Do not use laxatives to try to lose weight. They do not reduce body fat and misuse can be harmful.
- If you need laxatives regularly for more than a week or two, speak to your prescriber or GP
- If you have other symptoms, such as severe pain or vomiting, seek advice before taking a laxative
What about magnesium, probiotics and other remedies?
Magnesium supplements are widely discussed online for constipation. Some forms of magnesium do have a laxative effect. However, they are not suitable for everyone, particularly people with kidney problems, and can interact with other medicines. Ask a pharmacist first.
Probiotics have mixed evidence for constipation. They are unlikely to be harmful for most people, but should not replace the basics of fluid, fibre and activity.
Herbal "detox" or "slimming" teas often contain stimulant laxatives such as senna and are not recommended for regular use.
Should you reduce your dose?
If constipation is persistent or troublesome despite these measures, tell your prescriber.
Options may include:
- Staying on your current dose for longer before increasing
- Stepping down to a lower dose
- Reviewing your diet and other medicines
Do not stop treatment or change your dose without advice. For background on how doses are adjusted, see our Mounjaro dosage guide and Wegovy dosage guide.
Constipation, bloating and trapped wind
Constipation often comes with bloating and wind.
To reduce these:
- Increase fibre gradually
- Eat slowly and chew well
- Limit fizzy drinks
- Go easy on foods that commonly cause wind, such as beans, onions, cabbage and artificial sweeteners, if they bother you
- Try peppermint tea
- Take a gentle walk after meals
Burping and reflux are also common on these medicines. See our guide to sulphur burps and acid reflux on Mounjaro or Wegovy.
Constipation and haemorrhoids
Straining to pass hard stools can cause or worsen haemorrhoids (piles) and small tears called anal fissures.
Symptoms can include itching, discomfort, a lump around the anus, or bright red blood on the toilet paper.
Keeping stools soft is the best prevention. A pharmacist can advise on treatments for haemorrhoids.
Always get rectal bleeding checked by a GP, particularly if it is new, persistent or mixed in with the stool. Do not assume it is caused by piles.
What if you have diarrhoea instead?
Some people experience diarrhoea on weight loss injections, and some alternate between the two.
Occasionally, what appears to be diarrhoea is actually liquid stool leaking around a blockage of hard stool. This is called overflow diarrhoea and needs medical assessment.
If you have diarrhoea, focus on fluids and oral rehydration, and avoid taking laxatives. Read more in our guide to weight loss injection side effects.
When to seek medical help
Most constipation is uncomfortable but not serious. However, some symptoms need prompt attention.
Seek urgent medical help (call 111, or 999 in an emergency) if you have:
- Severe or persistent abdominal pain, especially if it spreads to your back
- A swollen, hard or very bloated abdomen
- Vomiting together with constipation
- Being unable to pass stool or wind
- Blood in your stool, or black, tarry stools
Severe abdominal pain can be a sign of pancreatitis, gallbladder problems or a blockage of the bowel. These are uncommon but serious, and should not be ignored.
Speak to your prescriber, pharmacist or GP if:
- You have not opened your bowels for several days despite trying the measures above
- Constipation is not improving after a week or two
- You need laxatives regularly
- You have unexplained weight loss beyond what is expected, or persistent changes in bowel habit lasting more than three weeks
- You are in pain when passing stools
How to prevent constipation from the start
If you are about to begin treatment, or about to increase your dose, a few habits can reduce the chance of constipation:
- Start increasing your fluid intake from day one
- Build fibre into every meal: a vegetable or fruit with each meal, and wholegrains where possible
- Add a daily walk
- Do not skip meals
- Act early. Do not wait several days before addressing it.
- Keep a suitable laxative at home, on a pharmacist's advice, in case you need it
How SynovaMed can help
If you are taking Mounjaro or Wegovy through SynovaMed and are struggling with constipation, please tell us in your check-in or contact our team. As a pharmacy, we can advise on suitable treatments and review your dose if needed.
You can find out more about how treatment is monitored through our weight loss programme.
Frequently Asked Questions
Does Mounjaro cause constipation?
Yes. Constipation is a common side effect of Mounjaro, particularly in the early weeks and after dose increases.
Does Wegovy cause constipation?
Yes. Around one in four people taking Wegovy in the main clinical trial reported constipation.
How do I relieve constipation on Mounjaro?
Drink more fluids, increase fibre gradually, stay active, do not ignore the urge to go, and ask a pharmacist about a suitable laxative if needed.
Can I take laxatives while on Mounjaro or Wegovy?
Yes, laxatives can generally be used for short-term relief. Ask a pharmacist which type is most suitable for you.
What is the best laxative for constipation on Wegovy?
There is no single best option. Osmotic laxatives such as macrogol are commonly recommended, but a pharmacist can advise based on your symptoms and medical history.
How long does constipation last on Mounjaro?
It is often worst in the first few weeks and after dose increases and improves for many people. Some people need ongoing dietary measures throughout treatment.
Is it normal to poo less on weight loss injections?
Yes, to some extent. If you eat less, you produce less stool. It becomes a problem if stools are hard, painful or difficult to pass.
Can fibre supplements help?
Yes. Bulk-forming fibre supplements such as ispaghula husk can help, but they must be taken with plenty of fluid.
Should I stop my injection if I am constipated?
Not usually. Most constipation can be managed. Speak to your prescriber if it is severe or persistent, as your dose can be reviewed.
When is constipation an emergency?
Seek urgent help if you have severe abdominal pain, a swollen abdomen, vomiting, are unable to pass stool or wind, or have blood in your stool.
Does drinking more water really help?
Yes. Adequate fluid keeps stools soft and helps fibre to work. It is the first step to try.
The bottom line: constipation on Mounjaro or Wegovy
Constipation is common on weight loss injections, but it is usually manageable.
The most effective steps are simple:
Drink more fluids.
Increase fibre gradually.
Keep moving.
Do not ignore the urge to go.
Use a suitable laxative for short-term relief, on a pharmacist's advice.
Tell your prescriber if it persists.
Seek urgent help for severe abdominal pain, vomiting, a swollen abdomen or blood in your stool.
With the right habits, most people find that constipation settles and does not stop them from continuing treatment.
Medical Disclaimer
This article is intended for general educational purposes and does not replace personalised medical advice, diagnosis or treatment. Always speak to a pharmacist or doctor before starting a laxative or supplement, particularly if you have other medical conditions or take other medicines. Mounjaro, Wegovy and other prescription weight-management medicines are not suitable for everyone. If you experience severe abdominal pain, persistent vomiting, a swollen abdomen, blood in your stool or other concerning symptoms, seek urgent medical attention.