What is the difference between Type 1 and Type 2 diabetes?

Type 1 diabetes (formerly juvenile/insulin-dependent diabetes): autoimmune destruction of pancreatic beta cells leads to absolute insulin deficiency. Onset usually in childhood/young adulthood but can occur at any age. Always requires insulin therapy. About 5-10% of diabetes cases. Higher risk of DKA. Symptoms typically develop quickly. Type 2 diabetes (formerly adult-onset/non-insulin-dependent): insulin resistance plus relative insulin deficiency. Onset typically in adulthood, but increasingly seen in younger people due to obesity. Strong association with obesity, sedentary lifestyle, family history. About 90-95% of diabetes cases. May be managed initially with diet, exercise, and oral medications (metformin first-line); often progresses to require insulin over years. Higher risk of HHS (hyperosmolar hyperglycemic state) than DKA. Symptoms often develop gradually. Both types have similar long-term complications: retinopathy, nephropathy, neuropathy, cardiovascular disease.