Why Wegovy (Semaglutide 2.4 mg) Causes Constipation: The Mechanism Explained

At a glance

• Labeled gut effect / Delays gastric emptying [1]
• Constipation rate / 24% vs 11% with placebo [1]
• Trial size / 2,116 on Wegovy 2.4 mg vs 1,261 on placebo, up to 68 weeks [1]
• Any GI reaction / 73% vs 47% [1]
• Severe reports / Ileus, intestinal obstruction, severe constipation with fecal impaction [1]
• Gastroparesis wording / Not recommended in severe gastroparesis [1]
• Dose schedule / 0.25 mg weekly in weeks 1 to 4, stepping up every 4 weeks to 2.4 mg from week 17 [1]

What the label says about the gut

Wegovy is a GLP-1 receptor agonist [1]. The label states that it delays gastric emptying and may affect absorption of oral medicines [1]. It lists constipation among the most common adverse reactions, at 24% in adults on 2.4 mg and 11% on placebo [1].

How common is constipation on Wegovy 2.4 mg?

The figures come from 3 placebo-controlled trials: 2,116 adults on Wegovy 2.4 mg and 1,261 on placebo, treatment up to 68 weeks [1]. Any GI reaction occurred in 73% vs 47% [1]. Nausea was 44% vs 16%, diarrhea 30% vs 16%, and vomiting 24% vs 6% [1]. Discontinuation for adverse reactions was 6.8% vs 3.2% [1]. The label names nausea, vomiting and diarrhea as the most common reasons for stopping; it does not give a separate discontinuation rate for constipation [1]. The 24% figure is pooled across the 2.4 mg trials, not reported by titration step [1].

What severe gut events does the label list?

The label warns that use has been associated with gastrointestinal adverse reactions, sometimes severe, and says Wegovy is not recommended in patients with severe gastroparesis [1]. Postmarketing reports include ileus, intestinal obstruction and severe constipation including fecal impaction [1]. Frequency cannot be estimated from voluntary reports [1].

These are not the same as the common 24% figure. The common figure is trial reporting; the impaction and obstruction reports are postmarketing events without a calculated rate [1].

Frequently asked questions

›Does Wegovy slow the whole gut?

The label's stated gut effect is delayed gastric emptying, which may affect absorption of oral medicines [1]. It does not state why constipation occurs [1].

›Does the dose change the constipation rate?

The label gives a pooled 24% rate for Wegovy 2.4 mg vs 11% for placebo [1]. In the two 72-week trials that added a 7.2 mg arm, constipation was 20% on 7.2 mg, 19% on 2.4 mg and 8% on placebo [1]. It does not give constipation rates for each titration step [1].

›Can Wegovy cause severe constipation?

Severe constipation, including fecal impaction, has been reported after Wegovy use, and the label also lists postmarketing reports of ileus and intestinal obstruction [1]. These voluntary reports cannot establish how often it occurs [1].

References

1. U.S. National Library of Medicine, DailyMed. Wegovy injection and Wegovy tablets (Novo Nordisk) prescribing information. Wegovy injection and Wegovy tablets (Novo Nordisk) label