The study aimed to evaluate the impact of selected polymorphisms in the IL6 (rs1800795) and INS (rs3842729) on the development of obesity and T2D, as well as to investigate the relationship between the specific genotypes and plasma glucose levels, serum IL-6 levels, serum insulin levels, serum glucagon levels, and serum C-reactive protein (CRP) levels. This evidence concerns the gene IL6 and obesity due to melanocortin 4 receptor deficiency.