Constipation on a GLP-1: What the Labels Report and What Actually Helps

Constipation is not a sign the drug is going wrong. It is one of the most common side effects of GLP-1 medicines, and the one that tends to last longest. The Wegovy label reports it in 24% of patients against 11% on placebo, and the Zepbound label reports it by dose — 17% at 5 mg, 14% at 10 mg, 11% at 15 mg, against 5%.^[1][2] What follows is what the evidence supports doing about it, and where the confident advice online runs ahead of what anyone has actually shown.

Why it happens, and why it does not fade like nausea

The labels say these drugs delay stomach emptying, and slower movement through the gut is the usual explanation for constipation: the longer stool takes to pass, the more water is drawn out of it. That explanation is plausible rather than proven. The authors of the pooled STEP analysis describe the cause of the stomach side effects as uncertain, note that the longer-acting drugs do not appear to delay emptying much, and point to a 20-week study of semaglutide 2.4 mg that found no measurable delay.^[6]

What is well established is that constipation behaves differently from nausea. Nausea is worst in the opening weeks and at each dose increase, then settles. Constipation lasts longer: in the pooled STEP trials the median episode ran 47 days on semaglutide against 35 on placebo, compared with 2 or 3 days for vomiting and diarrhea. It does ease with time, though. In STEP 4, where people stayed on semaglutide for more than a year, constipation became less common as the months went on.^[6] Our side-effect timeline shows the two curves side by side for each drug. Diarrhea, the opposite complaint on the same drugs, behaves differently again and has no settled explanation; see GLP-1 diarrhea: what has actually been tested.

There is a second cause that gets less attention, and it may matter more. Appetite suppression means eating less, and eating less usually means less fiber and less fluid. Some of what people experience as a drug effect is a diet effect the drug caused indirectly. That distinction matters, because one of those two things is straightforwardly fixable.

What the labels actually report

How common the serious end is

A 2023 analysis in JAMA looked at gastrointestinal adverse events among people taking GLP-1 medicines for weight loss rather than diabetes, and found elevated rates of the outcomes that matter more than discomfort — among them bowel obstruction.^[4] The absolute numbers were small, and the detail matters: the semaglutide group in that study had no obstruction events at all, the signal came from liraglutide, and the result lost statistical significance in one of the authors’ own re-analyses.^[4] A 2025 pooling of 55 placebo-controlled trials found the drugs probably have little or no effect on obstruction or ileus.^[7] Reassuring, but not a reason to ignore the warning signs below.

A 2026 comparative study in the Annals of Internal Medicine set dulaglutide, semaglutide and tirzepatide against each other on gastrointestinal safety in type 2 diabetes.^[5] Comparative work of that kind is what tells you whether switching drugs is a plausible answer to a gut problem, which is a question a great many people ask and very few sources answer with evidence.

What the evidence supports trying

The honest summary is that this has been studied far less than the confident advice suggests. What follows is ordered by how well supported it is, and the ordering is itself the useful part.

1. Put back the fiber the appetite suppression removed. This is the best-founded step, and it is a correction rather than a treatment — you are restoring an intake the drug quietly cut. Our fiber calculator works the target from the National Academies figures and steps you up about 5 g a week, because arriving at a high-fiber diet in one jump produces bloating and gas on top of everything else.
2. Water alongside it, not instead of it. Fiber without fluid makes stool bulkier and harder, which is the opposite of the goal. This is the step most often given alone and it is the one least likely to work alone.
3. Movement. Weakly supported for constipation generally, and worth doing for other reasons regardless.
4. Anything pharmacological is a prescriber conversation. Osmotic laxatives, stool softeners and stimulant laxatives are different drugs doing different things, some of which interact with how you are already taking a GLP-1. We are not going to name one.

What we could not find is good evidence on the question people most want answered: whether any of this works specifically for drug-induced slowed transit, as opposed to constipation in general. The guidance being applied is largely general-population guidance borrowed for a new situation. It is reasonable. It is not the same thing as having been tested here. A 2026 systematic review of randomized trials of dietary strategies alongside these drugs reached the same conclusion: stomach symptoms happened anyway, and the evidence on the best nutritional approach remains limited.^[9]

When the answer is the dose

Holding a dose longer before stepping up, or dropping back a step, is a real option and a common one. It is also entirely your prescriber’s to make — the labels build “as tolerated” language into the titration schedule precisely so a clinician can use it.

If that is the conversation you are heading into, go in with specifics: which dose you are on, how long you have been on it, how many days without a movement, and what you have already tried. Our titration planner will print the schedule from your drug’s own label so you can point at the step you are standing on.