Circus that's basically my experience, any kind of serious exercise just makes you feel awful after a few minutes. It is really annoying to realise that it isn't even diabetes that is causing this, exactly the opposite, it's the TREATMENT for the diabetes which is causing this, not that we have any choice.
I usually take 0.5 to 1 unit with breakfast because I am trying to eat low (well no) carb and I have to admit some sort of carb content for the peppers and onions in a vegetable omelette or whatever it is. Probably half a unit is still too much but I would rather be low than high given the long term risks. Before running I have tried eating apples (14g each) and so on but either it isn't enough or it isn't fast enough. Sometimes if I am below 6 before bed I will eat a couple of crackers (5.3g each) and they go in far faster but I would be terrified of trying to do that as a way to fuel running because you'd end up at some scary number before you knew it.
It just doesn't seem like there's any way to have enough fuel on board to actually do a half hour run, without the drugs ruining it. That's probably about what I used to do, half an hour each way. The only backup plan I have is to just keep sipping glucose drinks as I go but that seems very easy to get wrong and end up damaging yourself. At the end of the day it feels like there are a lot of things you can in theory do with diabetes, you can eat big slices of chocolate cake and meals with chapatis and white rice and you can go running. While I wouldn't want to speak for anyone else, for me the risks of doing these things outweigh the reward. And I do not say that lightly.