What is the distinction between autoimmune diabetes, Type 1 (T1) diabetes, and Type 2 (T2) diabetes?

From the Guidelines

Autoimmune diabetes is essentially the same as type 1 diabetes, characterized by the immune system mistakenly attacking and destroying insulin-producing beta cells in the pancreas, as supported by the most recent evidence from 2025 1. The distinction between autoimmune diabetes, type 1 (T1) diabetes, and type 2 (T2) diabetes is crucial for proper diagnosis and management.

• Autoimmune diabetes, or type 1 diabetes, is an autoimmune process that leads to insufficient insulin production, requiring lifelong insulin therapy.
• Type 1 diabetes typically develops in childhood or adolescence, though it can occur at any age, and is characterized by the presence of two or more islet autoantibodies and normoglycemia in stage 1, as described in the 2020 standards of medical care in diabetes 1.
• In contrast, type 2 diabetes is primarily caused by insulin resistance, where cells don't respond properly to insulin, combined with inadequate insulin production, and is strongly associated with lifestyle factors like obesity and physical inactivity, as noted in the 2024 standards of care in diabetes 1.
• Management of autoimmune diabetes requires insulin therapy from diagnosis, typically with multiple daily injections or an insulin pump, and blood glucose monitoring is essential, with target ranges typically between 80-130 mg/dL before meals and below 180 mg/dL after meals.
• The autoimmune nature of type 1 diabetes explains why it cannot be prevented or reversed through lifestyle changes alone, unlike many cases of type 2 diabetes which may improve with weight loss, exercise, and dietary modifications, as highlighted in the 2025 standards of care in diabetes 1. Key characteristics of type 1 diabetes include:
• The presence of two or more islet autoantibodies
• Normoglycemia in stage 1
• Dysglycemia in stage 2
• Clinical symptoms and diabetes by standard criteria in stage 3
• A 5-year risk of developing symptomatic type 1 diabetes of 44% overall, but varying considerably based on number, titer, and specificity of autoantibodies, as well as age of seroconversion and genetic risk, as reported in the 2024 standards of care in diabetes 1. It is essential to note that the diagnosis of type 1 diabetes does not preclude also having features classically associated with type 2 diabetes, and until more precise subsets are used in clinical practice, it may be appropriate to categorize such an individual as having features of both type 1 and type 2 diabetes to facilitate access to appropriate treatment, as suggested in the 2025 standards of care in diabetes 1.

From the Research

Distinction between Autoimmune Diabetes, Type 1 (T1) Diabetes, and Type 2 (T2) Diabetes

• Autoimmune diabetes is characterized by the immune-mediated destruction of islet insulin-secreting beta-cells, which can lead to Type 1 diabetes mellitus (T1DM) 2.
• Type 1 diabetes is a progressive autoimmune disease that starts long before a clinical diagnosis is made, with the American Diabetes Association recognizing three stages: stage 1 (normoglycaemic and positive for autoantibodies to β-cell antigens); stage 2 (asymptomatic with dysglycaemia); and stage 3, which is defined by glucose levels consistent with the definition of diabetes mellitus 3.
• Type 2 diabetes, on the other hand, is not typically considered an autoimmune disease, although there is a form of autoimmune diabetes that does not require insulin at diagnosis, known as latent autoimmune diabetes of the adult (LADA), which can be mistaken for Type 2 diabetes due to its initial non-insulin-requiring nature 2.
• The key distinction between T1DM and T2DM lies in their underlying pathophysiology, with T1DM resulting from autoimmune destruction of beta-cells and T2DM resulting from a combination of insulin resistance and impaired insulin secretion.
• LADA is characterized by the presence of autoantibodies to islet antigens, low insulin secretion, and a higher rate of progression to insulin dependency, similar to T1DM, but with an onset typically in adult life 2.

Characteristics of Each Condition

• Type 1 diabetes:
  • Characterized by autoimmune destruction of beta-cells
  • Typically requires insulin therapy from the time of diagnosis
  • Often diagnosed in childhood or adolescence
• Latent Autoimmune Diabetes of the Adult (LADA):
  • Characterized by autoimmune destruction of beta-cells, but with an initial non-insulin-requiring phase
  • Typically diagnosed in adult life
  • May progress to insulin dependency over time
• Type 2 diabetes:
  • Characterized by insulin resistance and impaired insulin secretion
  • Often associated with obesity, physical inactivity, and other metabolic risk factors
  • May be managed with lifestyle modifications, oral medications, or insulin therapy, depending on the severity of the disease.

Immunotherapeutic Approaches

• Immunotherapeutic approaches, such as proinflammatory cytokine inhibition, cell-depletion and cell-therapy approaches, autoantigen-specific treatments, and stem cell therapies, are being explored for the prevention and management of T1DM 4, 5.
• These approaches aim to preserve beta-cell function, reduce insulin dependency, and potentially alter the natural history of the disease 5.