Angie, who is 15 years old, asks, " My great-grandfather and great uncle both were insulin dependent diabetics. What are my chances of developing diabetes?"

Michael's reply:

Dear Angie,
Your chances of getting Type I diabetes are actually fairly small. The chance of any school-aged child getting Type 1 diabetes is 1 in 600 children.  If your parent had it, it would only be between 2-5 per 100 siblings. The chance of getting it with a great uncle and great grandfather having it is much less than 1 per 100 people. This is still greater than the "average person" getting it , but not much.
I wonder if your great grandfather really had Type I diabetes though.  Before 1921, no one survived the disease (we had not invented insulin until about 1921). Some Type 2 Diabetics do take insulin. If he was less than 40 years old when he was diagnosed, took insulin from the start, and was diagnosed after 1921, then he was probably Type 1.