23/10/2026
Constipation is one of the most common Mounjaro and Wegovy side effects, and one of the least talked about.
In the pooled Wegovy trials it affected 24.2% of people (vs 11.1% on placebo). It was mostly mild to moderate, with a median duration of about 47 days.
Why it happens: these medicines deliberately slow how fast your stomach empties. That's part of how they work, but slower transit plus eating less fibre can make for a sluggish bowel.
What many people find helps (and the HSE suggests): fluids first, fibre built up gradually (wheat bran, oats, linseed), a daily walk, and not ignoring the urge.
A short list worth memorising: severe or worsening belly pain especially with vomiting, no bowel movement for days with bloating, or blood in the stool. Contact a doctor promptly.
It's the kind of thing a doctor-supervised programme should help you with, rather than something to quietly tough out.
The full guide (sources included): https://slimbr.com/blog/mounjaro-wegovy-constipation-ireland