I’m running the NYC Marathon this November on behalf of Breakthrough T1D, and I’d love to hear from those of you who’ve tackled marathons (or other endurance races) while managing T1D. I have a few specific questions, and I’d be grateful for any advice, experiences, or resources you can share:
Carb Loading & Insulin Adjustments
How do you safely manage the 2–3 day carb-loading period before race day?
A significant increase in carbs requires more insulin precision, but I’m cautious about having too much insulin on board (IOB) within 24 hours of the race. How have you balanced this?
Fueling During the Race
What fueling methods or products do you rely on (UCAN, gels, fruit snacks, sports drinks, etc.)?
How often do you take carbs during the marathon, and how do you monitor/adjust insulin alongside it?
Given there are anywhere from 2-4 hours from waking up to actually starting the race, how many times do you eat / fuel pre-race? Are you turning your pump on exercise mode during the pre-race down time? Are you reducing insulin at all or keeping to your regular settings and adjusting 1 hour before?
Tandem t:slim X2 Update Question
Has anyone else noticed that after the most recent update, you can’t download full pump therapy data—only blood sugar data pulls in? Any troubleshooting tips or workarounds?
Any Other Tips?
Whether it’s pacing with T1D, pre-race routines, or post-race recovery, I’d love to hear your lessons learned.
Thank you so much in advance—this community has been such a valuable resource for me as I train!
@meghan_finley4Welcome Megham to the Breakthrough T1D Community Forum!
I admire, kind of jealous of, your ability to take on this challenge and wish you well. Tandem Source is working well with ALL data displaying properly for my fully updated t-Slim; I suggest that you contact Tandem Technical if you haven’t already done so.
hi @meghan_finley4 Meghan! welcome to Breakthrough T1d! I’m not going to pretend I’ve ever run a marathon marathon, but I have observations from working for 48 straight hours, and from intense exercise.
carb loading…. “normals” that is people with working endocrine systems, may carb load to encourage fat formation and to encourage glycogen storage. the way you encourage fat formation is to eat more than you exercise, and the way to store glycogen is to run your blood sugar a bit higher than 100 mg/dl the easiest way with a Tandem is to set your “exercise mode” because all that really does in set a BS target of 150 mg/dl. you can maximize glycogen by ensuring no fast drops in BS and maintaining a slightly higher average. Insulin useable life for us is 4-6 hours. unless you are using a long acting insulin which is not typical in pumpers.
google thinks you need 100g carbs per hour. I’m thinking juice and gels. your stomach isnt working normally when running, so eating a italian hoagie or fried chicken is probably a bad idea. Simple sugars absorb directly into your bloodstream even from your mouth. Glucose the simplest sugar and most readily absorbable, but it is so bad and likely a choking hazard so my go-to for endurance bicycle riding is gatorade and fruit juice.
the hardest thing is race day, having ANY IOB for me would mean I am only running 1 hour. I would consider disconnecting completely and then only adding fractional units to keep my bs 150 to 180. Exercise mode is useless and it will give me a 1.5u correction which for me would put me in the hospital during an enduro type exercise. When I ride, I am disconnected about 4+ hours before, I may reconnect if I see my bs rise but my correction factor is closer to 100 during exercise so I use insulin sparingly. during the race I might be tempted to reconnect so I dont forget but be careful the dumb thing may bolus you after drinking a juice.
I only use clarity I dont care what tandem is doing, after an update sometimes I have to re-login to get pump data to upload.
CGM is handy but useless. it tells you your blood sugar 15 minutes ago if you are running and see a drop it is already too late. keep gels on you so you can try to deal with low blood sugar. Still I LOVE G7 direct to apple watch! that’s a game changer for me.
after extreme exercise I do know my glycogen stores are likely empty and I may have to eat 100-200g to raise my blood sugar. I would carefully put my pump in exercise and watch it for 8 hours after a marathon race.
Initially I had the same thought as @Joe about carb loading not working for T1D, although for different reasons, but I found science that says it might work but no one has determined if carb loading or not carb loading leads to better performance for T1Ds. Carbohydrate Intake in the Context of Exercise in People with Type 1 Diabetes - PMC (section 6.3 is carb loading) Off the top of my head other factors that make generic advice less useful are women store and release energy better than men and if you are producing any insulin at all, or only recently stopped your metabolism isn’t going to be as messed up as mine after producing 0 insulin for 30+ years. I think you’re going to have to experiment during training, try a long run with and without it.
I hope some runners join the conversation. If you want expert opinions TCOYD is doing a Q&A tomorrow with two endos who have T1D. Dr. Edelman is a cyclist. If the time doesn’t work just email him, he’s amazing at replying. Another option, costs money, https://integrateddiabetes.com/ offers remote Diabetes Education services, they have educators that have T1D and are runners, I think women and men.
Have fun and after the race please tell us what worked for you!
I hope you beat your best time!!!