Although, it could be hypothesized that patients on insulin treatment may have a more advanced form of diabetes and therefore be at risk of a more severe form of COVID-19, our multivariate analysis found that metformin treatment was nonetheless a protective factor against severe COVID-19, regardless of the severity of diabetes (OR for severe COVID-19: 0.8, 95 CI: (0.5–0.9) metformin treatment vs. no metformin treatment; p = 0.048). The gene discussed is INS; the disease is diabetes mellitus.