There was high certainty of evidence that insulin use was related to a 33% increased risk of COVID-19-related death (SRR 1.33 [95% CI 1.18, 1.49], n=26 studies [ESM Fig. 27]), while metformin use was associated with a 31% decreased risk (SRR 0.69 [95% CI 0.60, 0.79], n=23 studies [ESM Fig. 28]). This evidence concerns the gene INS and COVID-19.