Constipation on GLP-1 medicines
Quick answer. Constipation is one of the most common side effects of GLP-1 medicines. A 2025 expert advisory puts it at 17% to 24% in trials, and pooled trials show people on the medicines were about two to three times as likely to report it as people on placebo. Fluids and food fiber come first, and experts list magnesium, fiber supplements and polyethylene glycol as options to ask about.
What it is
These medicines slow how fast the stomach empties, and eating less food means less bulk moving through the gut. Constipation tends to show up in the first weeks and after dose increases, and it often eases once the dose is stable. Severe belly pain, or vomiting along with constipation, is a reason to call your prescriber promptly.
What trials show
A 2025 review of 26 placebo-controlled trials in adults without diabetes found that digestive side effects were by far the most common ones. They affected 47% to 84% of people on the medicines compared with 13% to 63% on placebo. The most common were nausea, vomiting, diarrhea and constipation.
Pooled analyses give figures for constipation specifically, as relative risks compared with placebo. For tirzepatide in six trials of people without diabetes, the relative risk was 2.85. For once-weekly semaglutide in nine trials, the odds ratio was 2.43. Put plainly, constipation was roughly two to three times as likely as on placebo.
The Atlas did not find a randomized trial that tested a constipation treatment in people on these medicines. Advice on what to do comes from expert guidance.
What experts say to do
The 2025 advisory says to manage constipation early. It starts with fluids and fiber from food. It points out that foods high in protein, fat or fiber slow stomach emptying further, which can help weight loss but can also make constipation worse, so people sometimes need to ease off them for a while.
If food changes are not enough, it lists daily magnesium, with magnesium citrate described as effective and well tolerated and powders allowing the dose to be adjusted to keep bowel movements regular. Fiber supplements or capsules and polyethylene glycol 3350 may also help, and stool softeners can reduce straining. It notes that long-lasting constipation can lead to reactive diarrhea.
The advisory also stresses fluids in general. The official labels warn that vomiting, diarrhea and dehydration can lead to acute kidney injury, so drink enough and call early if you cannot keep fluids down.
What people report
Constipation is a constant topic in communities of people on GLP-1 medicines. The things people commonly say they try are more water, psyllium or other fiber, magnesium, stool softeners, prunes or kiwi fruit, coffee and walking. Some report that adding fiber too quickly made bloating worse, which fits the expert point that fiber slows stomach emptying.
People also commonly describe the problem as worst in the days after a dose increase, and as improving later. That matches the pattern in trials, but nobody has measured which of the tips works best.
This is people sharing what they do, not tested treatment. Many who post are happy with what worked for them, and the people it did not work for are less likely to post.
Who needs to be careful
- Anyone with kidney disease, since some products such as magnesium can build up and need medical guidance.
- Anyone with a bowel condition, past bowel surgery or a history of blockage.
- Anyone with severe pain, swelling or repeated vomiting, who should be seen promptly.
Questions to bring to a clinician or dietitian
- Which constipation treatment is safe with my other medicines and kidneys?
- How much fiber and fluid should I aim for?
- Should we slow the dose increases if this is bad?
- Which symptoms mean I should call you or be seen right away?
What is still unknown
- Which constipation treatment works best for people on these medicines is untested.
- How long constipation lasts after dose increases varies and is not well described.
- How the newer medicines compare on constipation is not yet clear.
Related pages
Sources
- Efficacy and safety of glucagon-like peptide-1 receptor agonists for weight loss among adults without diabetes: a systematic review of randomized controlled trials Moiz A, et al. Ann Intern Med. 2025;178(2):199-217. PMID 39761578. Funding: None reported. Journal article
- Efficacy and safety of tirzepatide on weight loss in patients without diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials Kommu S, et al. Obes Rev. 2025;26(11):e13961. PMID 40510020. Funding: Research support from the U.S. National Institutes of Health is listed. Journal article
- Efficacy and safety of once-weekly subcutaneous semaglutide on weight loss in patients with overweight or obesity without diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials Kommu S, Berg RL. Obes Rev. 2024;25(9):e13792. PMID 38923272. Funding: Research support from the U.S. National Institutes of Health is listed. Journal article
- Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and the Obesity Society Mozaffarian D, et al. Obes Pillars. 2025;15:100181. PMID 40673264. Funding: Professional societies; several authors report industry relationships. Journal article
- Wegovy (semaglutide) injection and tablets: prescribing information Novo Nordisk, on DailyMed (U.S. National Library of Medicine). Label version 6/2026. One label covers both the injection and the tablets. Official FDA label on DailyMed
- Zepbound (tirzepatide) injection: prescribing information Eli Lilly and Company, on DailyMed (U.S. National Library of Medicine). Label version 8/2026. Official FDA label on DailyMed