Are your sugars regularly high? It could be a sign your renal function is starting to struggle slightly or the cardiac system in terms of how strong the heart beats and fluid retention?
Do you have other health conditions besides diabetes? Are you overweight? A smoker? Drinker? Do you have a good diet?
There could be hundreds of reasons for it but it could be high BM's over a prolonged period.
Did you ask the question?
If they haven't acted on it, it can't be a huge issue for now?
I'd try to make healthy choices to help yourself and reduce your BM's if they are high and you could find it is rectified naturally.
If it was my son, I'd still be there now drilling them for answers and a working out a solution, so please, make a call and ascertain what you can do to help yourself. They will appreciate that anyway, don't sit back and accept that it's a natural progression of diabetes, it could be something else, or, if it is diabetes related, put the work in now, make the changes and do everything you can to maintain your health.
Good Luck, am cheering you on!!!