Hi Jack,
Well done on the weight loss! (assuming that it was intentional.
)
Blood glucose reacts to exercise in different ways, depending on the person, the meds, the fitness level and how strenuous the exercise is. There are several different factors in play, so it isn't possible to give hard and fast guidance - except to say that for people on powerful glucose lowering medication, then going below 4mmol/l is heading into hypo territory, so have some glucotabs or other hypo treatment at hand, in case you need it.
I would suggest that you start off gently, and monitor your blood glucose before, during and after your session.
Then you can adjust things for your next and subsequent sessions.
You will soon discover what each particular type of exercise (cardio, resistance, HIIT, etc.) does to you and your blood glucose.
Some people find that a snack before exercising is all they need. Others use things like glucotabs or jelly babies to drip feed glucose in tiny amounts during exercise, and others find that their blood glucose rises significantly, so they don't need snacks at all, and reduce their insulin before exercising.
Probably worth monitoring your blood glucose for a few hours after your first exercise sessions too, since the impact of exercise can persist for the rest of the day.
Hope that helps!