GLP-1 receptor agonists and tirzepatide slow gastric emptying and intestinal transit, and constipation is one of their commonest adverse effects. Add anything else that slows the gut — an opioid, an anticholinergic, iron, a calcium channel blocker — and the effect stacks.
Constipation is easy to miss because patients attribute it to eating less, and it rarely makes it into a consultation focused on HbA1c and weight. Yet it is one of the main reasons people quietly stop the drug.
- Ask directly about bowel frequency and straining at every review on a GLP-1 agonist or tirzepatide
- Review the medication list for other drugs that slow gut transit
- Advise fluid and fibre, and have a plan for an osmotic laxative before escalating the dose
- Treat abdominal distension with vomiting and absolute constipation as possible obstruction, not a side effect
Why it matters
Unasked-about constipation is a common, silent reason patients stop an effective drug.
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