Why Wegovy (semaglutide 2.4 mg) Causes Diarrhea: The Mechanism Explained

What the Label Documents

Diarrhea is listed among the most common adverse reactions of Wegovy, meaning it occurred in at least 5% of patients [1]. In the label's pooled analysis of 3 placebo-controlled trials in adults with obesity or overweight, up to 68 weeks, 2,116 adults received Wegovy 2.4 mg and 1,261 received placebo [1]. Diarrhea occurred in 30% versus 16%, and any gastrointestinal reaction occurred in 73% versus 47% [1]. Permanent discontinuation for diarrhea was 0.7% versus 0.1% [1].

What Wegovy Does to the Gut

Semaglutide is a GLP-1 receptor agonist, and the label says Wegovy delays gastric emptying [1]. The label does not say how that delay, or any other action of the drug, leads to diarrhea, and we found no study that tests a mechanism for Wegovy diarrhea.

What Else the Label Warns About

The label has a broader severe GI warning. Severe gastrointestinal adverse reactions occurred in 4.1% of adults on Wegovy injection versus 0.9% on placebo [1]. Wegovy is not recommended in patients with severe gastroparesis [1]. Postmarketing reports include ileus, intestinal obstruction, and severe constipation including fecal impaction [1].

The label warns about acute kidney injury due to volume depletion and says to monitor renal function in patients reporting adverse reactions that could lead to volume depletion [1]. In the Wegovy trials, acute kidney injury occurred in 0.4 versus 0.2 cases per 100 patient-years (7 versus 4 adults), more often in patients with prior renal impairment and during dose titration, often after GI fluid loss [1].

Does Dose Escalation Matter?

The label's adult weight-management schedule increases the Wegovy injection dose every 4 weeks: 0.25 mg for weeks 1 to 4, 0.5 mg for weeks 5 to 8, 1 mg for weeks 9 to 12, 1.7 mg for weeks 13 to 16, then maintenance from week 17 [1]. The recommended maintenance dose is 2.4 mg; 1.7 mg is also a maintenance dose [1]. A review of GLP-1 obesity therapies notes that GI adverse events with these drugs often can be mitigated by slow up-titration [2].