Type 2 diabetes is divided into several stages.

In general, the development of type 2 diabetes has clear stages, which can be simply divided into prediabetes and clinical diabetes stages.

Prediabetes refers to blood glucose levels higher than normal but not meeting the diagnostic criteria for diabetes. It includes impaired fasting glucose (fasting blood glucose 6.1–6.9 mmol/L) and impaired glucose tolerance (2-hour blood glucose 7.8–11.0 mmol/L after glucose loading). This stage represents a critical period for prevention, and some individuals may also have obesity, dyslipidemia, and other problems.

In the clinical diabetes stage, early on is mainly characterized by insulin resistance, with compensatory insulin secretion and no obvious symptoms; lifestyle interventions and medications targeting insulin resistance are the main treatment approaches. In the middle stage, insulin secretion becomes insufficient to compensate for the resistance, leading to gradually rising blood glucose levels and the emergence of symptoms such as polydipsia, polyphagia, polyuria, and weight loss. In the late stage, pancreatic beta cells are severely damaged, with near absence of insulin secretion, requiring exogenous insulin to maintain blood glucose control. Patients are prone to develop acute complications such as diabetic ketoacidosis or hyperosmolar hyperglycemic syndrome.