Type 1 diabetes, once known as juvenile diabetes or insulin-dependent diabetes, is a chronic condition in which the pancreas produces little or no insulin. Insulin is a hormone needed to allow sugar (glucose) to enter cells to produce energy. Different factors, including genetics and some viruses, may contribute to type 1 diabetes. Although type 1 diabetes usually appears during childhood or adolescence, it can develop in adults. Type 1 diabetes signs and symptoms can appear relatively suddenly and may include: Increased thirst Frequent urination Bed-wetting in children who previously didn't wet the bed during the night Extreme hunger Unintended weight loss Irritability and other mood changes Fatigue and weakness Blurred vision. Consult your doctor if you notice any of the above signs and symptoms in you or your child. The exact cause of type 1 diabetes is unknown. Usually, the body's own immune system — which normally fights harmful bacteria and viruses — mistakenly destroys the insulin-producing (islet, or islets of Langerhans) cells in the pancreas. Other possible causes include: Genetics Exposure to viruses and other environmental factors