Diabetes mellitus, which is commonly known only as diabetes, is characterized by abnormally high level of sugar in the blood.

Symptoms may not be present if the level of blood sugar is elevated only mildly. The basic symptoms of this disease are: excessive production of urine, increased fluid intake, excessive thirst, blurred vision, lethargy and sudden and unexplained loss of weight. The high level of sugar in the blood is due to the low level of insulin, which is a hormone secreted by the pancreas in order to maintain a normal blood sugar level.