Diabetes is considered a metabolic disorder that results when insulin concentrations are absent or reduced or when insulin action is impaired (referred to as insulin resistance). Without cellular uptake of blood glucose for energy, the balance of metabolizing carbohydrates, fats, and proteins for energy is lost. This results in hyperglycemia and the excess use of fats and proteins for energy production. The latter causes excess buildup of acetyl-CoA which is converted to ketone bodies or to cholesterol.
Polydipsia (increased thirst), polyuria (increased volume of urine), and unexplained weight loss are symptoms of diabetes. Polydipsia and polyuria occur as the body tries to lower blood glucose concentrations with increased urinary excretion of glucose. Weight loss results from increased utilization of proteins and fats for energy.
The image on the right represents impaired metabolism in diabetes. The thicker arrows represent the pathways that are imbalanced. In normal carbohydrate metabolism, the opposing arrows would be of the same size, representing a normal pathway and a balanced metabolism.