Good question and common problem. Constipation was reported in approximately 24% of participants in STEP 1 (vs 11% placebo), making it the second most common GI side effect after nausea.[1]
The mechanism: semaglutide slows gastric emptying and reduces overall GI motility. Combined with reduced food/fiber intake from appetite suppression, this creates a perfect storm for constipation.
Evidence-based approach, in order of escalation:
Step 1 — Lifestyle:
- Increase water to 100+ oz/day (not just 80)
- Soluble AND insoluble fiber — aim for 25-30g/day total. Psyllium for soluble, vegetables/bran for insoluble
- Daily movement — even walking increases colonic transit time
Step 2 — OTC osmotic laxatives:
- Polyethylene glycol (Miralax) — 17g daily, can take 3-5 days to see full effect. If you only tried it "for a few days" that may not have been long enough
- Magnesium citrate — 200-400mg daily as an osmotic agent
Step 3 — Stimulant laxatives (short-term):
- Bisacodyl (Dulcolax) or senna — for acute relief but NOT for daily long-term use
Step 4 — Prescription options:
- Linaclotide (Linzess) — prescription but very effective for GLP-1-related constipation
- Lubiprostone (Amitiza) — another option if Linzess doesn't work
[1] Wilding JPH, et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity." N Engl J Med. 2021.
Last edited: Jul 2, 2025 at 12:30 AM