Type 1 diabetes is commonly diagnosed in children and adolescence. Carlos developed type 1 diabetes because his body attacked itself (auto-immune damage), and damaged the organ that produces insulin, the pancreas.

Without type 1 diabetes, the pancreas constantly releases insulin to keep glucose levels stable and 'automatically' knows to release more when blood glucose levels exceed a certain threshold, such as during a meal (see diagram).

The special cells in his pancreas that make insulin are called β cells and they are now dead so he is not producing any insulin. This means that when Carlos eats, his blood sugar levels rise very high and stay high for a long time, because there is no insulin to reduce the glucose.