Just got told by my doctor over the phone that I am a diabetic. Do I have to tell my employer?

Background: I was having diabetic symptoms for about two weeks. Having my father, sister and brother all having been diagnosed as diabetics I pretty much knew what it was quickly. I had an a1c yesterday and today they called and said that I’m a diabetic.

Concern/Explanation: My concern right now (there are others but this is the most important to me) is do I have to tell my job that I am now a diabetic? I’ve worked too hard to get to where I’m at right now in life and I can’t bring myself to put my job at risk like that by telling them and then them potentially terminating me. It’s essentially all I have in life. Since learning I had the disease (a few hours ago), I was tasked with accepting that my career plans B, C and D were all now never going to be able happen anymore due to the disease. This is really going to mess my life up. So basically the only basket I have left is my current employer. I’ve worked with them for about five years and they are footing the bill right now for me to attend college. That degree, as well as the experience I’m getting from my job while getting the degree are my only gateways to success and at this point. I no longer have a fall back plan. I don’t want to lose my job. I’m willing to drop to a strict diet and do whatever it is I have to do to be well maintained with this disease. I’m not trying to be dramatic but if I don’t have my job, I’m probably going to die. Is this diagnosis something I have to disclose my employer? It’s probably worth noting, I work in security. I might be overthinking but I’m freaking out.

TLDR; my job is extremely important to me and essentially all I have. This illness has made it so that I no longer have career plans B, C or D. I don’t want to tell my employer and be considered unfit for work or be terminated because they think it could be considered a performance risk. Do I have to disclose the information to my employer? Is being fired even a real risk? How can I convince them that I won’t fail them and that I’m still strong enough to perform my function?