Evidence-graded answer
Does GLP-1 cause constipation?
Yes — about 20-25% of patients experience constipation during titration. Mechanism is delayed GI motility plus reduced food + fluid intake. Most cases resolve with fiber, fluid, and walking; some need short-term osmotic laxatives (polyethylene glycol).
Counterintuitively, the slowed gastric emptying that helps with satiety also slows the small intestine and colon, particularly during dose increases.
Self-management ladder: increase water, add 1-2 servings of soluble fiber daily (psyllium), walk 20-30 min/day. If those fail, polyethylene glycol 17 g daily is well tolerated and non-habit-forming.
Severe or persistent constipation (no BM 5+ days, abdominal distension, vomiting) warrants medical evaluation for partial ileus.