Making the correct diagnosis of type 1 and type 2 diabetes is crucial for appropriate management, with guidelines for these conditions recommending very different glucose-lowering treatment and education.1–3 These differences are predominantly driven by the rapid development of severe endogenous insulin deficiency in type 1 diabetes.1 This means that patients with type 1 diabetes need rapid insulin treatment and are at risk of life-threatening ketoacidosis without insulin treatment. This evidence concerns the gene INS and type 2 diabetes mellitus.