| Criteria | Type 1 Diabetes | Type 2 Diabetes | Remarks |
| Definition | Autoimmune destruction of insulin-producing β-cells in the pancreas | Metabolic disorder characterized by insulin resistance and relative insulin deficiency | Type 1 is insulin-deficient; Type 2 is insulin-resistant |
| Age of Onset | Commonly diagnosed in childhood or adolescence | Usually develops in adults over 40, but increasing in younger age groups | Age alone is not diagnostic; lifestyle plays a key role in Type 2 |
| Onset | Sudden and acute onset of symptoms | Gradual onset over months or years | Type 1 often presents with diabetic ketoacidosis initially |
| Etiology | Autoimmune origin; genetic and environmental triggers | Strongly associated with obesity, sedentary lifestyle, and genetic predisposition | Type 1 is autoimmune; Type 2 is multifactorial |
| Insulin Production | Little to no endogenous insulin production | Insulin may be produced but is ineffective due to resistance | C-peptide testing helps assess endogenous insulin levels |
| Insulin Requirement | Lifelong insulin therapy required | May be managed initially with lifestyle, then oral agents or insulin if needed | Type 1 patients are insulin-dependent from diagnosis |
| Body Weight | Typically normal or underweight at diagnosis | Frequently overweight or obese | Weight loss may be seen in both if uncontrolled |
| Autoantibodies | Autoantibodies (e.g., anti-GAD, IA-2) often present | Autoantibodies usually absent | Antibody testing helps differentiate Type 1 from Type 2 |
| Family History | Less commonly associated with strong family history | Strong familial aggregation | Genetic risk is higher in Type 2 |
| Ketoacidosis Risk | High; diabetic ketoacidosis (DKA) is common at presentation | Rare; may occur in severe cases or under stress | DKA is a diagnostic clue for Type 1 |
| Glucose Control Approach | Insulin injections, glucose monitoring, lifestyle modifications | Diet, exercise, oral hypoglycemics, possibly insulin later | Both require glucose monitoring, but treatment modalities differ |
