Constipation is a very common digestive side effect reported by some people using GLP-1 injections for weight management, such as Mounjaro and Wegovy.

While constipation can be uncomfortable, it is usually manageable and often improves as your body adjusts to treatment. This guide explains why constipation can happen, how long it may last, and what can help.

Why can GLP-1 injections cause constipation?

GLP-1 medicines affect how food moves through the digestive system. The same mechanisms that support appetite control can also slow bowel activity.

Slower gut movement

GLP-1 injections slow gastric emptying and intestinal movement. When stool moves more slowly through the bowel, more water is absorbed, which can make stools harder and more difficult to pass.

Reduced food intake

Many people eat less overall while on treatment. Eating less fibre or fewer meals can reduce bowel stimulation.

Changes in fluid intake

Some people drink less without realising, especially if appetite is reduced. Lower fluid intake can worsen constipation.

Dose changes

Constipation is more likely:

• When starting treatment
• After a dose increase
  
  

This often improves with time.

How common is constipation?

Clinical studies and prescribing information show that:

• Constipation is a very common side effect
• It is reported more often early in treatment
• Symptoms often reduce as treatment continues
  
  

Not everyone will experience constipation, and severity varies from person to person.

How long does constipation last?

For many people:

• Constipation is temporary
• It improves within a few weeks
• Symptoms may briefly return after dose increases
  
  

With simple lifestyle changes, most people can manage symptoms effectively.

What can help relieve constipation?

The following measures are commonly recommended and safe for most people using GLP-1 injections:

• Increase fluid intake

Aim to drink water regularly throughout the day. Adequate hydration helps keep stools softer.

• Gradually increase fibre

Foods such as:

• Wholegrains
• Fruits (e.g. berries, pears)
• Vegetables
• Pulses
  
  

Increase fibre slowly to avoid bloating.

• Stay physically active

Gentle movement, such as walking, helps stimulate bowel activity.

• Eat regular meals

Even smaller meals can help keep the digestive system moving.

• Don’t ignore the urge to go

Delaying bowel movements can worsen constipation.

Can laxatives be used?

Some people may benefit from short-term use of a mild laxative, but this should be discussed with a pharmacist or prescriber first to ensure it is appropriate and used safely.

When should you seek medical advice?

Contact a healthcare professional if:

• Constipation is severe or persistent
• You have significant abdominal pain
• You notice blood in your stool
• Constipation does not improve despite self-care measures
  
  

Your prescriber may review your dose schedule or offer additional support.

Should you stop your GLP-1 injection?

Do not stop prescription treatment without medical advice. Constipation alone is usually not a reason to stop treatment, and symptoms often improve with time and supportive measures.

Speak to a healthcare professional about GLP-1 side effects

If constipation is affecting your comfort or quality of life while using a GLP-1 injection, our clinical team can help.

Our qualified pharmacists and prescribers can:

• Confirm whether symptoms are expected
• Offer personalised management advice
• Review whether your treatment plan needs adjusting
  
  

Key message

Constipation is a recognised and usually manageable side effect of GLP-1 injections. It is linked to slower digestion and reduced bowel movement — part of how these medicines work.

With hydration, fibre, gentle activity and time, most people find symptoms improve.

Medical disclaimer

This information is for general guidance only and does not replace personalised medical advice. GLP-1 receptor agonists are prescription-only medicines and may not be suitable for everyone. Always follow the advice of your prescriber or pharmacist and report any concerning side effects.