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Constipation: the one that lingers

Nausea gets the attention, but constipation is the gut side effect that lasts. In the semaglutide trials the typical episode ran for weeks, not days. Most cases are a nuisance; a few become a blockage, and it helps to know which signs separate them.

By Dr. Chiranjeevi Peetla · Updated November 2026 · 5 min read · 8 sources, each linked

How common

On Wegovy 2.4 mg, 24% of trial participants reported constipation, against 11% on placebo.[1] On Zepbound it was 17%, 14% and 11% at 5, 10 and 15 mg, against 5% on placebo.[2] A meta-analysis of 50 semaglutide trials put the number needed to harm at 13: for every 13 people treated, about one extra person gets constipated because of the drug.[3]

Wegovy 2.4 mgsemaglutide · adults with obesity
24%
11% placebo
Zepbound 5 mgtirzepatide
17%
5% placebo
Zepbound 15 mgtirzepatide
11%
5% placebo

Share reporting constipation at least once, drug vs placebo, from the US labels.[1][2]

How long it lasts

In the pooled STEP 1 to 3 analysis, the median constipation episode lasted 47 days on semaglutide, against 35 days in people on placebo who had it. For comparison, the median nausea episode lasted 8 days and diarrhea 3 days.[4] Constipation also plateaued earlier, around week 10, rather than peaking at the end of the dose build-up.[4][5]

Why it happens

These drugs slow the movement of food through the gut, and people eat and often drink less, which means less bulk and less water in the bowel.[5][6] Reviews of drug-safety reports describe the same picture, and note that the rare severe cases (impaction, a bowel ulcer from hard stool) come from this end of the spectrum.[6] Exactly how much each piece contributes has not been measured.

What has been tested, and what has not

No randomized trial has tested a constipation remedy specifically in people on GLP-1 drugs. Clinical reviews list fluids, fibre, osmotic laxatives and dose adjustment as the usual approach, which is standard constipation care borrowed from other settings.[6][7] Expert consensus guidance suggests reducing the dose if constipation worsens.[7] Choosing any of these, and especially changing a dose, is a conversation with your prescriber or pharmacist rather than a forum decision.

When it is urgent

After the drugs went on the market, reports came in of ileus (the bowel stops moving), intestinal obstruction and severe constipation with fecal impaction.[1][2] In a large matched cohort, the combined rate of severe constipation, gastroparesis or bowel obstruction was 1.02 versus 0.75 per 100 people per year; the relative increase is real, the absolute risk about 1 in 100 a year.[8]

  • No bowel movement for several days with a swollen, painful belly
  • Vomiting, especially if you cannot keep fluids down
  • Unable to pass gas
  • Severe or worsening belly pain

Any of these together is a reason for same-day medical care, not a home remedy.[1][6]

Heard vs evidence

"It settles in a week like the nausea."
The median episode was 47 days, the longest of any gut side effect in the trials.[4]
"Tirzepatide is much worse for constipation."
The label rates are lower for Zepbound than for Wegovy. Drug-safety reports show more constipation reports for tirzepatide, but those reports cannot give rates.[1][2][6]

The short version

Short on the way. A 35-second captioned version of this page is in production for the Fewer Bites channel. It will be embedded here when it is live.

Questions to bring to your prescriber

Print these or screenshot them. They are conversation starters, not a checklist of things to do.

  • What is a reasonable plan for me if constipation starts, and which over-the-counter options are safe with my other medicines?
  • At what point would you want me to call: how many days, which symptoms?
  • If it keeps happening, would you consider a different dose or a slower build-up?

Education, not advice. This page explains what trials, labels and guidelines report. It does not tell anyone to start, change or stop a medicine. Your prescriber knows your history; this page does not.

Sources

Every number on this page traces to one of these. "Primary read" means the full paper or label was read; "abstract only" means only the abstract was available; "secondary" means the figure was taken from a named review.

  1. Novo Nordisk / FDA. Wegovy (semaglutide) injection and tablets, prescribing information, revised 06/2026. label
  2. Eli Lilly / FDA. Zepbound (tirzepatide) prescribing information, revised 08/2026. label
  3. Sillassen CDBS et al. Gastrointestinal adverse events of semaglutide: systematic review, meta-analysis and trial sequential analysis of 50 RCTs. BMC Med 2025. primary read via Fewer Bites gut dossier · meta-analysis
  4. Wharton S et al. Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg: post hoc analysis of STEP 1–3. Diabetes Obes Metab 2022;24:94–105. primary read · post hoc · industry-funded
  5. Fewer Bites nausea dossier, section 3.2 (onset and duration, summarising Wharton 2022 and the Zepbound label). secondary · dossier summary of primary sources
  6. De Fano M et al. Constipation with GLP-1 receptor agonists: pharmacovigilance and clinical review. Nutrients 2025. secondary · narrative review
  7. Gorgojo-Martínez JJ et al. Clinical recommendations to manage gastrointestinal adverse events with GLP-1 receptor agonists. J Clin Med 2022 (Novo Nordisk-funded). secondary · expert consensus
  8. Alkabbani W et al. Severe gastrointestinal events with GLP-1 receptor agonists: propensity-matched cohort. Diabetes Obes Metab 2026. abstract only · cohort

Side effects

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