Question: Does my employer have to know about my diabetes before or while I am employed?
Answer: It's not necessary for your employer, or your potential employer to know that you have diabetes. However, once you have a job and you're in the workplace I think someone at the workplace should know that you have diabetes, especially if you take insulin.
If you became hypoglycemic you might not be able to take care of yourself or you might act strangely. And it would be important for a co-worker to know this might be related to your diabetes and they could help you receive medical assistance. So I recommend that some people in the workplace know that a patient has diabetes; however, I think it's up to the individual to decide how many people in the workplace know that you have diabetes.