By 21 September, Infarmed had received 266 complaints since the start of the year regarding suspected adverse reactions to weight-loss and diabetes medicines, such as vomiting, diarrhoea and hair loss.

Infarmed also reveals that from 1 January 2024 to 21 September, 695 reports were recorded relating to the same medicines.

Increase in consumption

In the case of tirzepatide, the active ingredient in Mounjaro, which was first marketed in November 2024, the majority of reports relate to this drug: six in 2024, 295 in 2025 and 186 up to 21 September 2026.

As for semaglutide (Ozempic and Rybelsus), there were 12 reports in 2024, 46 in 2025 and 54 in 2026; whilst dulaglutide (Trulicity) accounted for 12, 21 and 21 reports, respectively.

Liraglutide (Victoza and Saxenda), meanwhile, fell from 31 reports in 2024 to six in 2025 and five this year.

“The reporting rate for suspected ADRs [adverse drug reactions] has remained stable over the years, with slight variations,” states Infarmed, noting that the fluctuations are more pronounced in the case of liraglutide, due to lower exposure to the substance, which means that each report has a greater impact on the rate.

The rise in reports comes at a time marked by increased use of these medicines. For example, tirzepatide rose from 10,689 packs supplied to pharmacies in mainland Portugal in 2024 to 424,768 in 2025. By June 2026, 395,369 packs had already been placed on the market.

Main complaints

As regards suspected ADRs, nausea was the most frequently reported reaction, with 98 reports. This was followed by vomiting (68), diarrhoea (61) and constipation (41).

Infarmed reports that the most frequent complaints relate to symptoms of vomiting, diarrhoea and constipation. A further 29 cases of reactions at the injection site, 27 of dizziness, 21 of headaches and 19 of hair loss were also reported. The list of recorded symptoms also includes tiredness, abdominal pain, weight gain and flatulence.

European monitoring

Since 2024, 19 cases have been identified involving terms associated with pancreatitis. Seventeen cases involve hepatobiliary disorders, and six fall into the category of renal and urinary disorders.

A further 276 cases have been identified with at least one suspected adverse reaction classified under the category of gastrointestinal disorders.

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