Kloser, I highly doubt you are getting very much from vaporizing sweet e-liquids. Most (if not all) e-liquids are sweetened using sugar alcohols (the sweeteners in sugar free foods or in the litte Pink/Blue/Yellow packets) not real sugar. You should ask the vendor you are purchasing from about this. Let them know you are a diabetic and they should have no issue disclosing what sweetener they use.
Vegetable glycerin is a sugar alcohol as well and contains a very small portion of carbohydrate (sugar to your body)
To be safe:
1. If you are already vaporizing then continue doing so, take your blood sugar levels after vaping. See if they are different, better yet post your results, I for one would be very interested.
2. Talk to your doctor about it. Tell him/her that you haven't changed your diet but your are now vaporizing and ask them to check your A1C and make sure that it is not affecting you.
3. If you don't already know the signs and symptoms of hyperglycemia, learn them and be on the look out for them always.
The worst case scenario is that e-liquid tweaks your blood glucose and your physician can adjust your medication to compensate for it.