You would only need to speak to a doctor only if you have suffered diabetic complications as this poses certain risks during exercise, but even then it doesn't prevent you from going ahead.
Probably best just get started and find out what works for you.
The general guideline is that exercise will most likely lower your blood glucose, so as always carry something fast acting like lucozade or dextrose tablets, or whatever works for you, that's especially advisable when doing some jogging. You will most likely find that you can reduce your quick acting insulin because you are doing exercise. You might even find you need to combine a reduction in quick acting insulin + consuming some carbs during exercise.
I regularly run 10k in the evening which I have built up to over the last 6 months. Exercise seems to have a really profound effect on my BGs, so in my case I need to reduce my novorapid (fast acting insulin), levemir (background insulin) AND take some fast acting carbs in during the run. A 10k run for me would go something like this:
6:30pm - evening meal - prepare by reducing novorapid by 3 and levemir by 3
7:20pm - check BG to make sure it is high enough (but not too high) for exercise, if high BG check ketones, if no ketones and BG high enough - I'm good to go!
7:30pm - start 10k run
after 5k - start taking a sip of lucozade (3/4 of a 35ml bottle) every half mile, or more if required
after finishing - check BG
I don't apply hard rules here, I adapt based on how fast I'm going, I suddenly got 3 minutes faster very recently so have now been finding I'm finishing the lucozade by 8k and getting into dextrose tablets to get through the exercise without hypo'ing, going to experiment with further reduction in novorapid next time round. My BG pre-exercise was 12.4, post exercise it was 5.9, after taking on 5 dextrose tablets + the lucozade last time I ran 10k.
Under "normal" circumstances, my BGs are steady in the evening.
