In all groups (Healthy, T1D, T2D) overall median (IQR) glucagon levels were significantly higher when measured with RIA than with the ELISA (72.13 pmol/L [53.28–90.57 pmol/L] vs. 8.55 pmol/L [5.90–12.35 pmol/L], p < 0.001). Here, GCG is linked to type 1 diabetes mellitus.