| The only time I believe it might be necessary is if an episode might cause a dangerous situation, tho I believe in the U.S. there have been lawsuits by truck drivers trying to keep their jobs. I don't think it's illegal not to, though. If you're in the U.S. I'd call the federal department of labor, and the dept of labor of the state you live in; it may be covered by either. I'd also check with a worker-sympathetic (as opposed to one usually hired by employers, since they often have different interpretations) lawyer before telling your employer.
Discrimination based on your diabetes would very likely be illegal, especially under the americans with disabilities act, if they treat you differently after telling them.
Let us know what you find out. | 
