Diabetic woman. Computer artwork showing sugar (white dots) entering the blood stream of a diabetic woman as she eats an apple. Some of the sugar is used by mitochondria (blue) to produce energy. A close-up of cells of the pancreas, which secrete insulin, is shown at lower centre right. Diabetes is a metabolic disorder in which either the production of the hormone insulin, which regulates blood glucose levels, is reduced, or the sensitivity of body tissues to insulin is reduced. This causes unused sugars to accumulate in the blood and urine.