I workout most days, either weights and walking or swimming. Working out typically lowers glucose for me. If my glucose is under 120 prior to a workout I will take 1 glucose tabs(4 units of carb)depending on my IOB (insulin on board i.e. 1 unit of IOB = 2 tabs). I also know that when I come out of the pool depending on how hard I worked I may need another so I keep glucose tabs in my swim bag. If I eat lunch and I know I'm going to work out I will cut back on my lunchtime bolus 1 unit which means I'm high at workout time and need no correction though I may be low when I finish. I always have glucose tabs available in the gym. The key is the insulin on board # and understanding what a certain exercise routine does to your blood sugar. Stay out of the emergency room. As a side note I am 67 years old and have been a diabetic for 20 years.
I see that this discussion is rather old but, hoping my reply can help somebody out. I would make a log of my bgs, testing at least 6 times a day, but def include before exercising, immediately after and hr by hr afterwards for at least 1 week. From that you should be able to see how ur bgs are behaving with your exercise. Then, adjust your basals from there. Since everyone, is different, you possibly will need to adjust a lot lower or higher, it is what YOUR BODY NEEDS. It's not right or wrong. There is no percentage straight across the board. I have to actually wait until after my morning exercise to correct because with the bolus, BOOM! My sugar will drop to the floor. AFter the intense working out, I also have to raise my basal for 3 hrs afterwards. Go figure...
Hope this helps someone!
It's my understanding that when doing vigorous workouts using a lot of muscle power, the liver delivers large amounts of sugar to those muscles, and explains why some are going high.