I was dx'd with Type 1 at age 29. Nothing makes you feel young like being dx'd with Juvenile Diabetes at that age!! LOL (I know they don't call it that anymore though
Truly, it can happen at any age. It's an auto-immune disorder. While it generally happens in childhood, it can happen at any age due to a bad case of the flu or extreme illness, or any other extreme stress on the body. I'm not sure what caused mine, but I believe it's because I was a "late" DES baby (my mother took DES, which went "out" in the early 60's, but unfortunately not with her doc, and she took it in the late 60's). DES has been found to cause many problems, with girls as well as boys of the moms that took it (although it is generally thought of to affect mostly the girls), one of which was auto-immune disorders in the children. Many have come down with lupus and rheumatoid arthritis, as well as Type 1 diabetes.
Anyway, I'm sorry you're going through this now. It sucks, no matter what age you get it at. Please find a great endocrinologist/dietican and CDE - it's a "team" disease, with YOU as the leader. I had to learn that early on. My dietician was fantastic - if you like tomatoes and melon and stuff like that. I don't, so I had to be assertive and let her know what I would eat, so she could help me plan meals around my favorite foods. Same with the CDE - if you let them know what YOUR schedule is, then they can help you plan when to eat/take your insulin/how much to take, etc.
It's hard at clinicals. I'm on an insulin pump now, which I love, and that has made it easier to control my B.S.'s. You know how crazy it is with meal times, and with the pump, there is a lot of flexibility in eating. It may be something to look into further down the road.
Please take care!