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About 24% of people on the semaglutide weight-loss dose get constipated — and it is the GI side effect that lingers longest, roughly 47 days on average. Here is the mechanism, a relief protocol that escalates sensibly, when it eases, and the red flags that mean stop and call.
The numbers: in STEP-1, constipation was reported by about 24% of people on semaglutide 2.4 mg (the Wegovy weight-loss dose) versus about 11% on placebo. On the lower diabetes doses used for Ozempic it is less frequent, roughly 5–15%. So it is genuinely common — and notably, the placebo rate is high too, a reminder that dieting and eating less by itself constipates people, not only the drug.
The mechanism is the drug’s whole point turned on your bowel. GLP-1s slow gastric emptying and gut motility so food lingers and you feel full longer. But slower transit means stool spends more time in the colon, where more water gets reabsorbed — so it arrives harder and drier. Add the fact that you are eating far less (often less fiber and drinking less), and the plumbing slows on both ends. It is the same slowed digestion behind the appetite effect, which is why you cannot fully separate the two.
Longer than nausea. Trial data put the average duration at about 47 days on semaglutide versus 35 on placebo. It is typically worst in the dose-escalation weeks — right after each step up — and often settles as your body adapts to a steady dose. If it is not improving on a stable dose, or it is getting worse, treat that as a reason to talk to your prescriber, not to keep waiting.
Rarely, slowed motility tips into a serious blockage — ileus or bowel obstruction — which the GLP-1 labels specifically flag. Get urgent care for severe or worsening abdominal pain, a hard or swollen belly, vomiting, or no bowel movement AND no passing of gas for several days. That combination is different from ordinary constipation and needs to be evaluated, not managed with more laxatives at home.
Constipation is one of several GI effects — see the full side effects by drug and symptom, and what to eat and avoid to keep symptoms down.