When food enters the body, it is broken down into glucose and transported by the blood to the cells. Cells use glucose for energy. To do that, the cells need to use the insulin secreted by the pancreas. If cells don't get enough insulin or can't use insulin effectively to absorb glucose, glucose stays in the blood and causes blood sugar to rise. When your blood sugar exceeds the threshold of 126 mg/dL, you are diagnosed with diabetes. Type 1 diabetes and type 2  Type-1-diabetes: Because your pancreas cannot secrete insulin. The cause is not known yet. Appears very early, possibly from birth. Manage only by taking insulin and controlling blood sugar. There is currently no cure.  Type-2-diabetes: Either the pancreas doesn't make enough insulin or it's due to insulin resistance. The cause may be overweight, inactivity, eating a lot of carbs, ethnicity... The disease appears later. Manage by diet, exercise, weight loss… Can be prevented or relieved.