Could it happen that a person using insulin to control diabetes still have a cdl license with passenger endorsement?

Varies Person&State: Like most legal issues, varies with both the law in each state & individual characteristics. Most people taking Insulin are type 2, a bad treatment option because it drives appetite, obesity & intermittent low glucose, sometimes dangerous to them & others. Thus check out the issues; stop all carb intake & if type 2: titrate up victoza, (liraglutide) +/- amylin, +/- metformin: far better tx & check state laws.

Type one dm: Using Insulin if deemed neccassary by your md should not be stopped to get cdl certain states allow a cdl but impose restrictions like monitoring, good control no hypoglycemia and good training to avoid danger to yourself and others.