Regarding the daily insulin requirement, as shown in Fig. 4a, the subgroup meta-analysis revealed a non-significant pooled estimate; − 2.25, 95% CI (− 4.812, 0.313), p = 0.085. This was also associated with a very high degree of heterogeneity among the 3 included T2DM studies, I2 score 96%. Here, INS is linked to type 2 diabetes mellitus.