Not sure what type you have, but i once had a diabetic student on microlights. He was limited to solo or with another qualified pilot, he had to take his blood sugar one hour before flying and then just before flying, and i believe if he flew more than an hour solo he was supposed to take a blood sugar reading in flight.
I'm not sure if this is the norm, or if you have better controlled diabetes then it would be different. Being limited to one hour flights in a microlight isn't all that bad, you can still get plenty done.