Diabetes Mellitus Types 1 and 2

Diabetes mellitus is persistent hyperglycemia caused by inadequate insulin action. Type 1 diabetes results from immune-mediated destruction of pancreatic beta cells, producing absolute insulin deficiency. Type 2 diabetes begins with insulin resistance and progresses to relative beta-cell secretory failure; insulin production may remain normal or high early in the disease, but it no longer meets metabolic demand. That distinction predicts treatment and danger. A person with type 1 diabetes cannot safely go without basal insulin because fat breakdown and ketone production accelerate rapidly. A person with type 2 diabetes usually has enough endogenous insulin to prevent ketosis, but severe illness, profound insulin deficiency, or an SGLT2 inhibitor can still precipitate diabetic ketoacidosis. Age, body size, and the presence of obesity help with pattern recognition but do not establish the type. Chronic hyperglycemia causes osmotic diuresis, vascular injury, and tissue glycation. Polyuria and thirst may be the first visible effects; kidney disease, retinopathy, neuropathy, cardiovascular disease, and impaired wound healing are later consequences. Management therefore has two simultaneous aims: restore safe glucose regulation and reduce the vascular and metabolic consequences of...