@Daletri,you want to work to find a "balance point" between carbs and basal adjustments that will allow you to stay relatively smooth for runs that stretch out to an hour and beyond. I've done a couple of marathons and 9 1/2s and have played around with different things. At first, I'd run my basal low, down to 10% having encountered someone who suggested that zero can lead to clogs when you fire it back up. A lot of times, I'd use 7 or 13% as they are lucky numbers (ha!). Then I'd bring along some carbs. At first, I'd use 2x bottles, on an Amphipod belt, and have high-octane Gatorade using the powder, to pack it with like 45G of carbs and lower strength with just 10 for hydration.
Eventually, I found myself tinkering with this and reducing the stronger to 20-25 which is close to normal strength. This was as I was getting into marathon training, with a group, that had lots of discussion of nutrition, the importance of snacks along the way, etc.and it felt good to already be doing what I needed to do as far as that went. I also got a suggestion from @Jerry_Nairn about RaceReady shorts, that have a pocket that holds a meter very conveniently
Eventually, I discovered that w/ the moderately strong Gatorade, I could turn up my basal, as I'd noted post-run highs and found what worked for me was 50-75% and I tinker while I go. If my BG runs up, I'll turn the basal up and down, I'll turn it down. Eventually, I found a very nice balance point, about 8-12G of carbs/ 3 miles. I think this works out to a bit less than Gary Scheiner's suggestion from "Think Like a Pancreas", which is where I got a lot of my theories about these things. It really boils down to getting out and getting going and testing to see what's happening. I started using CGM right before my first 1/2 Marathon and it was immensely helpful, although it fell off 3 miles into the first one, before I discovered Opsite Flexifix. Now, if I run 5K after work (I've been a slacker lately!), I can have a glass of skim milk and get a "predicted high" alert about a mile into it and a "predicted low" as it "cooks off" as I get home.
I looked up Addison's and ketoacidosis but didn't find any specifics as to whether the steroids might cause that independently of BG. I usually assume no KA w/o elevated BG so if my BG is cool I don't check for it.
Finally, I do notice that adrenaline on race days totally makes my BG go crazy!! I bolused and didn't eat anything for the first 17 miles of the 2012 Chicago Marathon as my BG was quite high. Then it "broke" and I chowed down the rest of the race....eeek!!