My grandmother has has type 1 diabetes for more than 25 years (she's now 79 years old). My mother died when I was a kid, so I don't have any information about her health.
I want to know my what are my chances of getting diabetes and how can I prevent it?
Being diagnosed with type 1 diabetes (DM1) at the age of 54 is very rare. It's usually diagnosed in children or teenagers and used to even be called 'juvenile diabetes' because of that. The reason it's usually diagnosed this early is because it comes from the body's inability to produce insulin in the pancreas after the immune system has destroyed these cells. But it's not totally unheard of to be diagnosed late. (I'm just including this because the answer for type 2 diabetes would be different)
Inheritance
Diabetes isn't inherited in any kind of simple pattern. You can't say "if a parent has it, the child will have it with a 50% probability" - or even that a child of two people with DM1 will have DM1 themselves.
The Joslin Diabetes Center has a few numbers:
If an immediate relative (parent, brother, sister, son or daughter) has type 1 diabetes, one's risk of developing type 1 diabetes is 10 to 20 times the risk of the general population
The risk for a child of a parent with type 1 diabetes is lower if it is the mother — rather than the father — who has diabetes
Since you don't know whether your mother had it, your risk is even harder to judge.
Prevention
There are risk factors other than genetics for DM1, but unfortunately generally, type 1 diabetes can't be prevented. There are a few trials about this, the one I could find about injecting children with insulin was unsuccessful.
The good news is that if you are worried about having diabetes, testing isn't very complicated and can be done regularly with no adverse effects.
