Constipation on Ozempic®

Constipation in the trial tables

Constipation is the fifth row of Table 1 in the US label, which lists reactions reported by at least 5% of people on Ozempic® and more often than on placebo. The trials enrolled adults with type 2 diabetes using Ozempic® alone or with basal insulin for about 30 weeks ^[1]. Europe classes constipation as common, between 1 in 100 and 1 in 10 people, and Canada reports it from a seven-trial pool with a mixed placebo and active comparator group ^[2][3].

An uneven dose pattern

Most stomach reactions in the Ozempic® tables either rise with the dose or stay level. Constipation was a little more common on 0.5 mg than on 1 mg in both the US and the Canadian pools. Neither document offers a reason, and it would be guesswork to supply one. What both show clearly is that the two doses sat above the comparison group ^[1][3].

The US label’s sentence about reactions clustering during dose escalation names nausea, vomiting and diarrhea, not constipation, so the same timing should not be assumed. The European information adds a different time signal: in SUSTAIN 9, where semaglutide 1 mg was added to an SGLT2 inhibitor, constipation was reported by 6.7% on semaglutide and by no one on placebo, and its prevalence did not fall over time ^[1][2].

Rarer, more serious bowel reports

Section 6.2 of the US label lists reactions reported since semaglutide reached the market. Under the stomach and bowel heading it includes severe constipation with fecal impaction, ileus and intestinal obstruction. These reports come in voluntarily from an unknown number of users, so the label says their frequency cannot be reliably estimated and a causal link cannot always be shown ^[1]. Canada lists intestinal obstruction, including ileus and small bowel obstruction, among its post-market reports, and Europe lists intestinal obstruction with frequency not known ^[2][3].

Severe stomach and bowel reactions of all types were reported in 0.4% on 0.5 mg and 0.8% on 1 mg in the US trials, with none on placebo ^[1].

What research says about blockage

Two kinds of study point in different directions, which is worth knowing before reading headlines. A 2025 meta-analysis of 55 placebo-controlled randomised trials with 106,395 participants found that GLP-1 medicines increased gallstones and probably reflux, but probably had little or no effect on the risk of intestinal obstruction, paralytic ileus and most other serious stomach and bowel events ^[4].

A 2023 US insurance-claims study compared people without diabetes who started semaglutide or liraglutide for weight loss with people starting bupropion-naltrexone. The GLP-1 group had a higher risk of bowel obstruction (adjusted hazard ratio 4.22). Of the 613 semaglutide users, none had a recorded bowel obstruction; the events came from liraglutide users, and the study could not confirm why each medicine was prescribed ^[5]. Observational studies like this show associations, not proof of cause.

Why it may happen

What the label supports: semaglutide delays stomach emptying a little in the early period after a meal, and constipation is a recognised reaction above placebo ^[1].

What is plausible but unmeasured: none of the official documents says why constipation occurs. Eating less, which is part of how the medicine works for many people, could also mean less fibre and fluid, but no Ozempic® document tests that link.

General background: NIDDK lists not eating enough fibre, not drinking enough liquids, low physical activity, changes in routine, travel and certain medicines among common causes of constipation, and names diabetes among conditions that can contribute ^[6].

Other things that can cause it

• Medicines and supplements such as antacids containing aluminium or calcium, iron supplements, some blood pressure medicines (calcium channel blockers), diuretics, opioid pain medicines and some antidepressants ^[6].
• Slow movement through the colon, pelvic floor problems and irritable bowel syndrome ^[6].
• Hormone and metabolic conditions such as hypothyroidism and diabetes ^[6].
• Changes in daily routine, travel, pregnancy or ignoring the urge to go ^[6].

What may help

The Ozempic® documents give no specific advice for constipation beyond asking you to raise any side effect that bothers you or does not go away ^[1]. NIDDK’s general guidance for adults is a reasonable place to start a conversation with your prescriber or pharmacist ^[7].

• Eat more high-fibre foods, and drink plenty of water and other liquids, especially if you add fibre or a fibre supplement ^[7].
• Get regular physical activity ^[7].
• Give yourself time to go, use the bathroom as soon as you feel the urge, and some people find a set time after breakfast helps ^[7].
• If you suspect another medicine or supplement, talk to your doctor rather than stopping it yourself ^[7].
• Laxatives come in several types, and NIDDK says a health professional can advise which to use and for how long; stimulant laxatives are for severe constipation or when other options have not worked ^[7].

Details worth noting

Helpful details include how many days pass between bowel movements, whether stools are hard or painful to pass, whether there is bloating or pain, whether you can pass gas, what you have been eating and drinking, any new medicines or supplements, and whether the change began after starting Ozempic® or after a dose increase. A list like that turns a vague complaint into something your clinician can act on.

Ozempic® is a registered trademark of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.