If you do not mention you are Diabetic and something happens in the work place, your employer can be found to be negligent, insurance will be revoked and the company would then have no other choice but to come to you personally to seek remedy and possibly damages. Also not informing your employer you suffer from diabetes is lying and tantamount to Gross Misconduct.
So that dream job you studied for and worked hard in getting would flitter away because you were not truthful on your application, I don't need to explain the ramifications of trying to get another job with Sacked for Gross Misconduct on your employment record and unfortunately because of social media even if you miss it off your CV, someone will find out about it.
Weigh up the Pro's and Con's before omitting your illness, make an informed decision rather than one based on shame.
Diabetics are not disabled! We have a lifetime illness, not a disability.
Also remember we are lied to by politicians, by councils, and by the medical profession and we do not like it, so why would you do the same, employers want honest employees, you are a representative for their company and in turn their livelihood.
You would not give your bank details to a fraudster so why employ a liar