Here's a link to what the EEOC says about diabetes:
Questions and Answers About Diabetes in the Workplace and the Americans with Disabilities Act (ADA)
I agree wholeheartedly with Mcgriff. Document everything. That's the key to success. Disability discrimination lawsuits are not looked upon favorably by juries. Most employers will settle these cases way before getting to the courtroom, where a jury can punish them with multi-million dollar judgments.
Also, employers may not retaliate against employees for asking for accommodation.
If you can't afford an employment lawyer (and they are expensive), try contacting your local bar association and ask if they have a program where lawyers will provide services at a reduced rate or for free.
Best wishes for your good health.