Hmm, I would have used the achievement in my younger days in fact I did to success for one of my first jobs. However, that was probably more down to dumb luck on my part and a sympathetic interviewer.
However, I don't think I'd use it now, having more experience with senior managers, hiring managers and HR I feel admitting to a serious health condition that puts you at risk of increased sick days and so on is a not a wise move in the current job market.
There are hundred upon hundreds of applicants for mosts jobs. I'm sure I read about 2000 applicants for barista openings at a new coffee house local to me in the South of England, most of which I am sure were degree educated, volunteers etc.
When you're picking apples from apples any negative flag is likely to get you put on the "no" pile.
I would always keep achievements work related and perhaps have one personal that could only be viewed positively.
Most interviews are just a box ticking exercise, so i'd advise playing the game.
The above site highlights good ways to structure achievements in a way that most HR departments like. Have a few prepared before interview that you can fall back on.
Perhaps not strictly ethical and it comes down as to whether you view diabetes as a disability, but the best way it to put down that you have a disability on the application, this increases you likely hood of getting an interview as some organisations have quota to reach on this and you're often more likely to get an interview if you're marked as having a disability. If they can see that you can tick a disabled box, but are effectively healthy and in control this could be a form of positive discrimination.
I know it's bad, but I also know from contacts in HR that it happens!
So swings and roundabouts :)
Just be aware of the risks of disclosing in the interview and judge the situation accordingly. It probably depends on the employer and the industry as well.