How is pre-diabetes different from diabetes?

Blood Sugar. Pre-diabetes is defined as elevated blood sugars above normal but below the threshold for diagnosing as true diabetes. Some ranges place pre-diabetes as fasting blood sugars between 100-126. The american diabetes association reports that approximately 11% of pre-diabetics develop diabetes over the next 3 years and most will by approximately 10 years.
A1C level. In pre-diabetes, enough Insulin is still being secreted to control the blood sugar level. But the pancreas is burning out. Typically, a blood test called A1c is between 5.5-6.5. In diabetes, the Insulin no longer can control the blood sugar and the A1c is above 6.5.
Definition. People with prediabetes have blood sugar levels higher than normal but lower than in diabetes. They have an elevated risk of developing diabetes, and also appear to have an elevated risk of certain diabetic-type complications such as heart attack.