Type 1 diabetes develops when the insulin-producing cells in the body have been destroyed and the body is unable to produce any insulin.
Type 1 diabetes accounts for about 10 per cent of all adults with diabetes and is treated by insulin injections, a healthy diet and regular physical activity.
Type 1 diabetes can develop at any age but usually appears before the age of 40, and especially in childhood. It is the most common type of diabetes found in childhood.
Insulin is a hormone. It works as a chemical messenger that helps your body use the glucose in your blood to give you energy. You can think of it as the key that unlocks the door to the body's cells. Once the door is unlocked, glucose can enter the cells where it is used as fuel. In Type 1 diabetes the body is unable to produce any insulin so there is no key to unlock the door, and the glucose builds up in the blood.
The body can't use glucose to provide energy and tries to get it from elsewhere and starts to break down stores of fat and protein instead. This can cause weight loss. Because the body doesn't use the glucose it ends up passing into the urine.
Nobody knows for sure why these insulin-producing cells have been destroyed, but the most likely cause is the body having an abnormal reaction to the cells. This may be triggered by a virus or other infection.