Diabetes is a chronic disease characterized by an abnormally high blood sugar (glucose) level. This condition is caused by the inability of the body to properly convert glucose into energy, owing to a decreased production of a hormone called insulin. A persistently high blood sugar level increases the risk of several health problems. For example, persistent damage to glomerular capillaries of the kidney may lead to diabetic nephropathy, and damage to blood vessels in the retina may lead to diabetic retinopathy. Suppressing the increase in blood sugar level is effective not only in preventing the development of new health problems, but also in slowing down the progression of diabetic morbidities that have already developed.