Constipation is the GLP-1 side effect that outlasts the others. In the semaglutide weight-loss trials, an episode of diarrhoea typically ended within three days; an episode of constipation ran for a median of 47 days. It is also common: in the Wegovy trials, 24% of people on the drug reported it — against 11% of people on dummy injections, which is the reminder that a sizeable part of every figure below is not the drug at all.
This page sets out the constipation rate printed in nine current US labels, the placebo rate in the same table, and what the trial record says about how long it lasts. The labels were read on 11 October 2026 from DailyMed, using the manufacturers' own versions. It reports what the documents record; it does not advise on treatment, and anyone with persistent symptoms should speak to their prescriber.
The rate in every current label
Each label prints constipation in its adverse-reaction table, or in the text beneath it when the rate falls under the table's cut-off. The "excess" column is glp1ledger's subtraction — the drug rate minus the placebo rate in the same trial pool — which no label prints.
| Label (effective date) | Trial population | Placebo | Drug, by dose | Excess over placebo |
|---|---|---|---|---|
| Wegovy injection (2026-06-18) | Adults with obesity or overweight | 11% | 24% (2.4 mg) | 13 points |
| Wegovy injection, 7.2 mg trial | Adults with obesity | 8% | 19% (2.4 mg) · 20% (7.2 mg) | 11–12 points |
| Wegovy injection, adolescents | Ages 12 and older with obesity | 2% | 6% (2.4 mg) | 4 points |
| Zepbound (2026-08-28) | Adults with obesity or overweight | 5% | 17% (5 mg) · 14% (10 mg) · 11% (15 mg) | 6–12 points |
| Saxenda (2026-02-25) | Adults with obesity or overweight | 8.5% | 19.4% (3 mg) | 10.9 points |
| Foundayo tablets (2026-07-29) | Adults with obesity or overweight | 9% | 20% (5.5 mg) · 27% (9 mg) · 24% (17.2 mg) | 11–18 points |
| Mounjaro (2026-08-27) | Adults with type 2 diabetes | 1% | 6% (5 mg) · 6% (10 mg) · 7% (15 mg) | 5–6 points |
| Ozempic injection (2026-06-01) | Adults with type 2 diabetes | 1.5% | 5% (0.5 mg) · 3.1% (1 mg) | 1.6–3.5 points |
| Semaglutide tablets, Rybelsus/Ozempic (2026-01-30) | Adults with type 2 diabetes | 2% | 6% (7 mg) · 5% (14 mg) | 3–4 points |
| Victoza (2025-10-14) | Adults with type 2 diabetes | 1% | 5% (1.2 mg) · 5% (1.8 mg) | 4 points |
| Trulicity (2026-06-16) | Adults with type 2 diabetes | 0.7% | 3.9% (0.75 mg) · 3.7% (1.5 mg) | 3.0–3.2 points |
Trulicity's figures are from the text under its placebo-pool table, where reactions below 5% are listed. Zepbound's row counts "constipation" and "feces hard" together, according to the table's footnote.
Three things stand out in the table:
- Constipation does not follow the dose the way nausea does. On Zepbound it falls from 17% at 5 mg to 11% at 15 mg; on Ozempic, 1 mg sits below 0.5 mg; on semaglutide tablets, 14 mg sits below 7 mg; and Foundayo peaks at its middle dose. In the same Zepbound table, nausea, diarrhoea and vomiting all rise with dose. The labels give no explanation. One possibility the data cannot exclude: the figures count anyone who reported constipation once, and people on the higher doses spent their first weeks on the lower ones.
- The weight-loss trials record two to four times more constipation than the diabetes trials, on both arms. Placebo groups in the weight trials reported it at 5% to 11%, against 0.7% to 2% in the diabetes trials. Comparing a Wegovy figure with an Ozempic figure compares two populations, not two drugs.
- The excess over placebo is similar across the weight-loss drugs — roughly 6 to 18 points — whatever the molecule.
How long it lasts — the one side effect measured in weeks
No label prints how long constipation lasts on its own drug. The fullest figures come from a pooled analysis of the STEP 1, 2 and 3 trials of semaglutide 2.4 mg, the Wegovy dose (Wharton et al., 2022):
| Side effect | Reported, semaglutide vs placebo | Median length of one episode, semaglutide | Median, placebo |
|---|---|---|---|
| Constipation | 24.2% vs 11.1% | 47 days | 35 days |
| Nausea | 43.9% vs 16.1% | 8 days | similar |
| Diarrhoea | 29.7% vs 15.9% | 3 days | similar |
| Vomiting | 24.5% vs 6.3% | 2 days | similar |
The paper adds two details no label carries. The share of people with constipation rose and then levelled off at about week 10, rather than peaking and falling with the dose-escalation weeks as nausea did; and in people who stayed on semaglutide in the STEP 4 trial, the prevalence of constipation decreased gradually over time. The authors suggest the longer episodes "may be because of the effects of GLP-1RAs on GI motility", while noting that for constipation and diarrhoea, "evidence is lacking" on the mechanism.
Two cautions on the 47 days. It is a median across reported episodes, so half lasted longer; and the placebo median was 35 days, which says that constipation, once it starts, tends to last weeks in this population whatever the injection contained. The drug adds frequency and roughly 12 days to the typical episode, on these figures — not the whole of it.
The timeline for every common stomach symptom side by side is on the side-effect timeline page; diarrhoea, which runs on a much shorter clock, has its own page.
What the labels say about serious bowel problems
Every one of the nine labels read for this page lists, among postmarketing reports, "ileus, intestinal obstruction, severe constipation including fecal impaction". The labels state that such reports come from a population of uncertain size, so it is not possible to estimate their frequency or establish that the drug caused them. They are therefore a signal recorded by the regulator, not a rate: the trials above do not contain enough of these events to count.
The patient Medication Guides put the practical line plainly: stomach problems, "sometimes severe, have been reported", and the guides for Zepbound, Wegovy, Mounjaro and Ozempic each tell readers to contact their healthcare provider about stomach problems "that are severe or will not go away". The labels' other stomach-related warnings — on pancreatitis and gallbladder disease — are set out on GLP-1 and pancreatitis and GLP-1 and the gallbladder.
How many people stop because of it
Labels report discontinuations for stomach side effects as a group, not for constipation alone. In Zepbound's pooled trials, 1.9%, 3.3% and 4.3% of people on 5, 10 and 15 mg stopped treatment because of gastrointestinal reactions, against 0.5% on placebo; in the STEP pool, 4.3% on semaglutide did. How those figures compare across the class is on the GLP-1 with the fewest side effects, and the overview of every side effect is on GLP-1 side effects.
What this page cannot tell you
- The excess figures are subtractions within one table, not adjusted estimates, and they carry the uncertainty of both arms.
- "Reported" means reported at least once during the trial, at any severity. The rates are not the share of people constipated at any given moment, and they do not distinguish a single hard stool from weeks of symptoms.
- The episode lengths come from one drug at one dose (semaglutide 2.4 mg). No trial has published the same measurement for tirzepatide, and the Zepbound label's falling dose pattern means its figures should not be assumed to behave the same way.
- No trial compared two GLP-1 drugs for constipation in a way any label reports, so the table ranks nothing.
- Compounded and research products were not studied in any of these trials.
Whether constipation on a particular medicine calls for a change of plan is a decision for the prescriber.
Sources
- Prescribing information read on DailyMed, 2026-10-11 (manufacturer label versions, effective dates as shown): WEGOVY (Novo Nordisk, set ID ee06186f-2aa3-4990-a760-757579d8f77b), adult, 7.2 mg and adolescent adverse-reaction tables and section 6.2; ZEPBOUND (Eli Lilly, 487cd7e7-434c-4925-99fa-aa80b1cc776b), Table 1; SAXENDA (Novo Nordisk, 3946d389-0926-4f77-a708-0acb8153b143), Table 2; FOUNDAYO (Eli Lilly, 8ac446c5-feba-474f-a103-23facb9b5c62), Table 1; MOUNJARO (Eli Lilly, d2d7da5d-ad07-4228-955f-cf7e355c8cc0), Table 1; OZEMPIC injection (Novo Nordisk, adec4fd2-6858-4c99-91d4-531f5f2a2d79), Table 1; semaglutide tablets, OZEMPIC/RYBELSUS (Novo Nordisk, 27f15fac-7d98-4114-a2ec-92494a91da98); VICTOZA (Novo Nordisk, 5a9ef4ea-c76a-4d34-a604-27c5b505f5a4); TRULICITY (Eli Lilly, 463050bd-2b1c-40f5-b3c3-0a04bb433309), section 6.1 text and 6.2. All at dailymed.nlm.nih.gov.
- Wharton S, Calanna S, Davies M, et al., "Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg in adults with overweight or obesity, and the relationship between gastrointestinal adverse events and weight loss", Diabetes, Obesity and Metabolism 2022;24:94–105, PMC9293236.