That is a really good question and I will be interested in what others have to say. I was diagnosed at age 40 and my grandmother had T2 diabetes. I wasn't seeing a doctor between the ages of 30-40 and I don't remember if I had an A1C done when I was diagnosed 10+ years ago. I could have had diabetes for several years.There is a strong consensus among the medical community that genetics play a significant role in why people become type 2 diabetics. Type 2 diabetes appears mainly in the middle age normally after the age 40. (Nowadays, many young people, some even in their teens are diagnosed type 2 but it is still an exception to the rule.) Why is it that the genes responsible for type 2 diabetes choose to "express" themselves mainly after age 40?