You medical history and the fact that you are diabetic isn't necessary to go onto a CV.
A lot of employers require you to complete an application form or health questionnaire prior to or once you have accepted a role. It is completely to your own discretion whether you mention it during an interview.
I usually mention it during mine as I'm interested in asking about the companies policy towards medical appointments, it also gives me a chance to explain that I would always provide a lot of notice before an appointment and that I try to have mine as early or as late as possible in the day and I will always make up the time as necessary.
Every employer / interviewer I have had (barring one, whom became my boss after I'd worked at the company for 1.5 years) have been perfectly reasonable (whether I'm just lucky or not, I don't know), I've always found honesty is best. Make sure you inform your employer once you have accepted a role though, to not mention any medical condition that could affect working performance (could include diabetes due to high / low BG Levels and how it may effect you) could be considered breach of contract
Best of luck with everything!
