Managing BG Levels During My First Half Marathon

Kelsey Bonilla Health Guide
  • Not only did I complete my first half marathon, but I ran faster than I'd hoped!


    On Valentine's Day, I awoke early to get ready. My gear was all laid out (including a new running jacket that fit snuggly and had pockets for my continuous glucose monitor, glucose tablets, and insulin pump); and my breakfast planned ahead of time. During my training, I rarely ate before a run, but given that the race didn't start until 8:00 a.m., I wanted to eat something. I had a banana with some natural peanut butter and bolused conservatively. Fortunately, my fasting blood sugar was 110 mg/dl; I'd been concerned about high blood sugars and the potential need to give a correction bolus prior to the race.

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    Once I was dressed and fed, I awaited my ride. Appropriately, since this race was to mark the milestone of the thirtieth birthday, my mom accompanied me.


    Nerves had settled in as we made the trip north to the race site. My blood sugar had started to rise, then leveled off and dropped a bit. Just before we arrived, my blood sugar was 123 mg/dl. I dreaded the thought of going low during the race so I ate half of a nutritional bar. About 90 minutes prior to the race, I'd set a temporary basal rate to last for 3 hours. My normal basal pattern is .75 units/hour from 6:00 a.m. to 8:00 a.m. and then switches to .50 units/hour. For the race, I went with .40 units/hour.

    It was a beautiful day; already around 65 degrees at the beginning of the race and expected to be in the low 70s later that morning. I was well hydrated, my blood sugar was stable, and my legs felt strong after a week of tapering my run length. Mentally I knew that everything was aligned for a good run.


    The one question that kept burning in my mind was: how fast had I been running outdoors? Since I trained throughout the winter and early in the morning, many of my runs were done on the treadmill. My mile times had gotten faster throughout my training so I knew I could easily run nine minute miles on the treadmill. However, I wasn't sure how that translated to outdoor running. I assumed I wasn't running as fast, but I really didn't know.


    I felt a huge rush of excited energy as I lined up for the start of the race. Just before the guy went off, they warned us that every hill we ran down on the way out, we'd be running up on the way back. That was a nice mental trick to play on everyone!


    The first mile was a gradual decent into a canyon and I kept reminding myself not to run too fast. My goal was to run slower than necessary for the first few miles so I wouldn't get caught up in feeling good and burn myself out early. I was surprised when the first mile time was announced as I ran by: 9:40.


    The race progressed from there. At each mile marker I noticed that I was keeping a steady pace of about 9:30. I checked my continuous glucose monitor every couple miles and learned that it was holding steady at 160 mg/dl, which was higher than I wanted to be. I gave a correction bolus of .35 units around mile 5. Just after the turnaround point, my blood sugar was still over 150 mg/dl, so I did another correction bolus of .25 units.

  • With four miles left, I felt great. I knew I was running a good pace and would certainly finish the race. I enjoyed the company of my fellow runners and felt a great sense of accomplishment that I'd set a goal and was in the process of achieving it.

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    The final mile was tough. We had to run up the gradual hill that we descended at the beginning of the race. Those last few minutes of running weren't fun. When I saw my mom cheering as we approached the final hundred meters, I got a huge surge of energy and ran through the finish line. The time displayed when I finished was 2:03.50. I later learned my time translated into a pace just under nine and a half minute miles.

    My blood sugar was 140 mg/dl at the end of the race. I was slightly puzzled that my blood sugar hadn't dropped more during the extended exercise, until I read an interview with cross-country skier and type 1 diabetic, Kris Freeman. He mentioned that he gives himself a large bolus of insulin just before a race to combat the glucose spike caused by adrenaline his body produces during competition. That explains it!


    I feel better prepared for managing my blood sugar during future races. I imagine that I'd feel even more energy if my blood sugar was about 30-40 points lower throughout the race. But, for this time, I'm glad that my blood sugar didn't spike too high or drop too low during the race.


    I'm definitely hooked on running now. I looked into some marathons in the days following this race. While there are several in my area over the next few months, it's time for me to focus on another goal: getting pregnant!



Published On: March 09, 2010