Cagrilintide is investigational and not approved as a standalone therapy. The rates below are from supervised clinical trials of pharmaceutical-grade product with gradual dose escalation — conditions gray-market use does not reproduce.
Overview
Cagrilintide's side effects are dominated by the gut: in its 706-person phase 2 trial, gastrointestinal adverse events — mainly nausea, constipation, and diarrhea — affected 41–63% of participants across doses, versus 32% on placebo, with nausea alone reported by 20–47% (Lancet 2021). These effects were mostly mild-to-moderate and concentrated early in treatment. No unexpected safety signal emerged, but the compound has not completed the large phase 3 program that defines a drug's full safety profile as a standalone agent.
The trial rates, with numbers
From the phase 2 dose-finding trial:
- Any GI adverse event: 41–63% on cagrilintide (dose-dependent) vs 32% on placebo.
- Nausea: 20–47% across the 0.3–4.5 mg dose range.
- Constipation and diarrhea: among the most frequent events after nausea.
- Injection-site reactions and reduced appetite (partly the intended effect) were also reported.
In the phase 1b co-administration study with semaglutide, GI complaints likewise made up the largest share of adverse events (37% of all events), mostly mild-to-moderate, and the combination was judged to have an acceptable safety profile (Lancet 2021).
Why the gut bears the burden
The side effects are the mechanism, overshooting. Amylin signaling slows gastric emptying and promotes satiety through the hindbrain — push those levers hard and food sits longer, fullness becomes nausea, and bowel habits shift. The dose-dependence in the phase 2 data — GI rates climbing from 41% toward 63% as doses rose — is exactly the pattern a mechanism-based side effect produces. This is why trials escalate the dose slowly over months: the same amount that is intolerable as a starting dose is manageable after stepwise adaptation. It is also why abrupt, full-dose use of gray-market product tends to reproduce the worst of the trial side effects without the supervision.
In combination with semaglutide
Most people encountering cagrilintide will encounter it inside CagriSema, where amylin and GLP-1 mechanisms stack — and so do their GI effects. In the 68-week REDEFINE 1 phase 3 trial, gastrointestinal events affected 79.6% of participants on the combination versus 39.9% on placebo, though they were predominantly transient and mild-to-moderate (NEJM 2025). Details on the combination's profile are on the CagriSema side-effects page.
Open questions and unregulated product
Standalone cagrilintide has no completed phase 3 program of its own, so rare events and long-term effects (including the class questions that follow any potent weight-loss agent — gallbladder disease, muscle-mass loss, effects when combined with glucose-lowering drugs) remain incompletely characterized. Some of that gap is closing indirectly: the 68-week REDEFINE 1 trial included a 302-person cagrilintide-alone arm alongside the combination, which will extend the monotherapy safety record as its analyses are published. Until then, the deepest standalone dataset is 26 weeks long. And every reassuring number above describes verified pharmaceutical product given with slow escalation and monitoring: vials sold online as "cagrilintide" carry unverified identity, dose, and sterility on top of the molecule's open questions, and their users typically skip the very titration that kept trial side effects manageable. A clinician, not a vendor page, is the right place to weigh individual risk.