The present disclosure describes methods for treating or preventing Type 1 diabetes mellitus in juveniles, particularly in juveniles newly diagnosed with Type 1 diabetes. This prevention or treatment of Type 1 diabetes is achieved by administering one or more therapeutic agents to a juvenile in need, wherein the therapeutic agent is, for example, a competitive inhibitor of mevalonate synthesis, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, or an inducer of AMP protein kinase (AMPK) activity. In certain embodiments, juveniles with Type 1 diabetes are treated with an HMG-CoA reductase inhibitor such as a statin, thereby decreasing the destruction of islet cells, or maintaining endogenous insulin production, in the juvenile.