Diabetes: A comprehensive review of the Indian landscape in contrast with global trends

Table 2 Classification of diabetes, highlighted by the American diabetes association

Classification of diabetes
Ref.		Joseph et al[10], 2022; International Diabetes Federation[30], 2025
Diabetes type	Etiology/pathophysiology	Clinical and diagnostic features
Type 1 diabetes mellitus	An autoimmune-mediated destruction of pancreatic β-cells, often involving islet cell autoantibodies (e.g., GAD65, IA-2); this leads to absolute insulin deficiency; affects both children and adults, including latent autoimmune diabetes in adults (LADA)	Acute onset with symptoms like polyuria, polydipsia, weight loss, and fatigue; ketoacidosis is common at presentation; diagnosed by low C-peptide levels, presence of autoantibodies, and fasting hyperglycemia
Type 2 diabetes mellitus	Characterized by insulin resistance and a progressive decline in β-cell function; influenced by obesity, sedentary lifestyle, age, and genetic predisposition; often preceded by prediabetes (impaired glucose tolerance or fasting glucose)	Insidious onset, often asymptomatic for years; commonly diagnosed via routine screening; associated with metabolic syndrome; HbA1c ≥ 6.5%, fasting glucose ≥ 126 mg/dL, or 2-hour OGTT ≥ 200 mg/dL
Gestational diabetes mellitus (GDM)	Glucose intolerance is first recognized during pregnancy, typically in the 2nd or 3rd trimester; caused by hormonal changes leading to insulin resistance (e.g., placental lactogen, estrogen, cortisol)	Screened between 24-28 weeks of gestation using OGTT; usually asymptomatic but can lead to macrosomia, preeclampsia, and neonatal hypoglycemia; increases lifetime risk of T2DM

GAD65: Glutamic acid decarboxylase 65; IA-2: Protein phosphatase-like islet antigen 2; LADA: Latent autoimmune diabetes in adults; HbA1c: Glycated hemoglobin; OGTT: Oral glucose tolerance tests; GDM: Gestational diabetes mellitus; T2DM: Type 2 diabetes mellitus.