First, a clarification: The one hour fast requirement contained by Canon 919 of the Code of Canon Law applies to receiving Communion, not going to Mass, that is, the Church generally wants people to fast for one our before actually receiving the Eucharist, not before arriving at Mass. As a result, for most people, this fast can be satisfied more or less by simply not eating on the way to Mass!
But to respond to your situation, Canon 919 also states in part that "anyone who suffers from any infirmity" is not bound to observe the eucharistic fast. Even though you do not look or feel sick, diabetes obviously is an infirmity, the proper control of which requires you to follow a pattern of planned eating.
If your diet requires you to eat at such a time that you cannot observe the one-hour fast, you should have no scruples about approaching the Eucharist anyway, even if you might have been able to find another Mass at which the one hour fast could have been satisfied.