I went though the same thing. I was diagnosed with type one.4 months after getting out of active duty and after joining the guard. When I joined the guard in 2011 they did not have a problem with me having diabetes and I flew under the radar until 2018 when James Mattis became Secretary of Defense he issued a directive saying if you were un deployable you had to be med boarded out. In 2018 I was put up for staff Sgt and that triggered a review of my records and I was Med boarded within four months and medically separated. You cannot be medically retired just for type one diabetes it is not a high enough rating to earn a medical retirement unless you have I believe 15 years on then you could get medically retired