Autoimmune diabetes is a heterogeneous disease, encompassing both type 1 diabetes, characterized by fast progression towards an insulin-dependent state, and latent autoimmune diabetes in adults (LADA), considered a less severe form of autoimmune diabetes with a mild metabolic decompensation. An extensive genetic, phenotypic, and humoral heterogeneity is recognized even within the group of people with LADA. In this review, we discuss the pathological and clinical heterogeneity of autoimmune diabetes, highlighting the current understanding and gaps in knowledge.