Managing complications in Type 1 diabetes (T1D) remains challenging. HLA genes, particularly DR and DQ, are linked to T1D susceptibility. We studied 48 Japanese T1D inpatients and revealed associations between DRB1*04:05-DQB1*04:01 and DRB1*09:01-DQB1*03:03 haplotypes and complications, offering a new perspective for future research.