Can Mounjaro cause constipation or diarrhoea?

Yes—Mounjaro (tirzepatide) can cause both constipation and diarrhoea, and these are among its most common side effects, especially when starting treatment or increasing the dose. UK guidance notes that gastrointestinal effects like nausea, diarrhoea, constipation, and vomiting are usually mild to moderate, tend to occur during dose escalation, and often lessen over time, though they can lead to dehydration if severe. In studies, diarrhoea has been reported more often than constipation, with meta-analyses estimating diarrhoea in about 16% and constipation in about 3% of people taking tirzepatide, indicating a real but generally manageable risk. If symptoms are persistent, severe, or accompanied by signs of dehydration (such as dizziness or reduced urination), seek medical advice and consider reporting side effects via the MHRA Yellow Card scheme as advised in UK materials and patient leaflets.^[1][2][3][4]

• Mounjaro can cause both constipation and diarrhoea, particularly when starting or raising the dose.^[1][4]
• These gut side effects are usually mild to moderate and often improve with time.^[1][4]
• Diarrhoea appears more common than constipation in clinical data on tirzepatide.^[2]
• Severe symptoms can lead to dehydration; seek medical help if this occurs.^[3][4]
• UK materials advise reporting side effects through the MHRA Yellow Card scheme.^[3][4][5]

Sources

• NICE – Tirzepatide discussion aid for healthcare professionals and patients [1]
• Systematic review/meta-analysis of tirzepatide efficacy and safety (includes GI adverse events) [2]
• MHRA Drug Safety Update – GLP-1 receptor agonists: potential side effects & safety reminders [3]
• Mounjaro (tirzepatide) UK Patient Information Leaflet (emc) [4]
• Diabetes UK – About Mounjaro (GLP-1) and side effects [5]