- metabolism was significantly higher in T1D patients than in the patients with T2D and in healthy volunteers, - no change in metabolism between T2D and controls, - CYP1A2 activity was 34 and 42% higher in patients with T1D compared with controls and patients with T2D respectively but these changes did not reach the statistical significance (p = 0.11), - no change between groups concerning the CYP2D6 phenotype distribution. This evidence concerns the gene CYP2D6 and type 1 diabetes mellitus.