The most common Mounjaro side effects in clinical trials included nausea, diarrhoea, decreased appetite, vomiting, constipation, indigestion, and stomach pain.

In a 2023 comparative study of Mounjaro with the weight loss drug Mounjaro, nausea and vomiting were reported for about 1 in 5 people with each of the medications. Gallstones were reported for roughly 1 in 6.

The manufacturers also warn that Mounjaro may cause serious side effects, including inflammation of the pancreas, low blood sugar, serious allergic reactions, kidney problems, stomach problems, and changes in vision.

Patients are advised to stop using Mounjaro immediately in the event of serious symptoms, such as severe stomach pains or a strong allergic reaction, and to seek medical attention.