In a cohort of 31,966 patients with diabetes in Lombardy, researchers investigated if metformin use is associated with coronavirus disease 2019 (COVID-19) outcomes.

• Using a COVID-19 linkable administrative regional database, researchers selected patients with diabetes who were aged 40 years or older and had at least two prescriptions of antidiabetic drugs in 2019 and a positive test for severe acute respiratory syndrome coronavirus-2 from 15 February 2020 to 15 March 2021.

• There appeared a significantly lower risk of total mortality, in-hospital mortality, hospitalization for COVID-19, and ICU admission in correlation with metformin use vs metformin non-users.

• The findings suggest that metformin might be a potentially valuable drug to prevent severe COVID-19 disease, and support continuing prescribing metformin to COVID-19 patients with diabetes.