Therefore, the aim of this study was to investigate the association of the HMOX1 gene promoter area GTn length repeat, two different single nucleotide polymorphisms (− 413A/T (rs2071746) and + 99G/C (rs2071747), and serum HO-1 concentrations with vascular complications and all-cause mortality in individuals with T1D. The gene discussed is HMOX1; the disease is type 1 diabetes mellitus.