Update: Today was marathon day (half-marathon for me), and I did it! I finished! Here's the story:
Woke up at 5:00, and although my numbers had been good while I slept, I shot up to 175 for no reason as soon as I woke up (according to the CGM). I did a blood test to verify, and yes, that was right. I took one unit of Humalog, which brought me down to 125, almost literally right away. That is not normal for me.
Got ready, and my brother was here at 6:00 for us to go downtown to the start line, with my husband. I ate a Snickers Marathon Nutrition bar on the car ride, with no bolus taken for it. I should also mentioned I turned down my basal to "OFF" at 6:00, and didn't turn it back on until after the race was over.
We lined up around 6:40, and my CGM said 83. Then 72. Really?? I hadn't bolused for the bar I ate, and that was 22g of carb! This is where I panicked a bit. I ended up eating two Clif Shot gels - also about 25g of carb each - before the start. By the time we got to the starting line around 7:15, I was shooting back up, and was 157. I thought, "Awesome! Don't know what happened there, but at least I'm back up where I want to be, now."
Fast forward to mile 2 - I notice I'm over 200. Okay, not panicking yet. I "peaked", or so I thought, around 280 and then it showed that I was coming back down pretty quickly. Again, as a precaution, I ate another gel. This may be where my biggest mistake was, because I didn't drop too much more after that. In fact, I did most of the race over 300, and a good chunk of it "HIGH", which means I was over 400. I started taking a unit here and there after mile 8, not wanting to overdo it and drop too quickly.
By the 12th mile, I was back down to the 300's, so I was probably about 325 when I finished. Who knows how high I really got - but I tested before and after the race, and the CGM was accurate both of those times - so I have to believe those numbers are true.
It feels so good to know I was able to finish. I was very slow, and didn't run as much of it as I walked, but I finished, darn it - and that was the point. Finish, no passing out or throwing up. Check, check and check! Thinking of all of you guys on here and the support I've received definitely made a difference, and motivated me to push harder than I thought I could.
Man, do my feet hurt! :)