# Marathon Training + T1D: NYC Marathon Questions on Carb Loading, Fueling & Tandem **URL:** \ **Category:** Physical Activity Support\ **Created:** [September 22, 2025, 12:02am UTC](https://forum.breakthrought1d.org/t/marathon-training-t1d-nyc-marathon-questions-on-carb-loading-fueling-tandem/74950 "2025-09-22T00:02:55Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![meghan\_finley4](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.breakthrought1d.org/meghan_finley4/32/5505_2.png) [@meghan\_finley4](https://forum.breakthrought1d.org/u/meghan_finley4)\ **Post date:** [September 22, 2025, 12:02am UTC](https://forum.breakthrought1d.org/t/marathon-training-t1d-nyc-marathon-questions-on-carb-loading-fueling-tandem/74950/1 "2025-09-22T00:02:55Z")
Hi everyone, 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: 1. **Carb Loading & Insulin Adjustments** 2. **Fueling During the Race** 3. **Tandem t:slim X2 Update Question** 4. **Any Other Tips?** Thank you so much in advance—this community has been such a valuable resource for me as I train! —Meghan ---
**Author:** ![Dennis](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.breakthrought1d.org/dennis/32/5527_2.png) [@Dennis](https://forum.breakthrought1d.org/u/Dennis)\ **Post date:** [September 22, 2025, 1:22pm UTC](https://forum.breakthrought1d.org/t/marathon-training-t1d-nyc-marathon-questions-on-carb-loading-fueling-tandem/74950/2 "2025-09-22T13:22:36Z")
@meghan_finley4 _ **Welcome 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. Good Luck!!! ---
**Author:** ![joe](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.breakthrought1d.org/joe/32/2937_2.png) [@joe](https://forum.breakthrought1d.org/u/joe)\ **Post date:** [September 22, 2025, 2:17pm UTC](https://forum.breakthrought1d.org/t/marathon-training-t1d-nyc-marathon-questions-on-carb-loading-fueling-tandem/74950/3 "2025-09-22T14:17:43Z")
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. good luck 🍀 ☮ 😀 I hope you beat your best time!!! ---
**Author:** ![spdif](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.breakthrought1d.org/spdif/32/5548_2.png) [@spdif](https://forum.breakthrought1d.org/u/spdif)\ **Post date:** [September 23, 2025, 7:26pm UTC](https://forum.breakthrought1d.org/t/marathon-training-t1d-nyc-marathon-questions-on-carb-loading-fueling-tandem/74950/4 "2025-09-23T19:26:20Z")
Someone at the NYC Breakthrough T1D chapter wrote a series of posts on what worked for them: [strimble, Author at Greater New York Metro Chapter](https://www.breakthrought1d.org/greaternymetro/author/strimble/) 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](https://pmc.ncbi.nlm.nih.gov/articles/PMC6950062/) (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](https://tcoyd.org/type-1-diabetes-expert-qa/september/live/) 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/](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! ---
**Author:** ![spdif](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.breakthrought1d.org/spdif/32/5548_2.png) [@spdif](https://forum.breakthrought1d.org/u/spdif)\ **Post date:** [December 3, 2025, 8:36pm UTC](https://forum.breakthrought1d.org/t/marathon-training-t1d-nyc-marathon-questions-on-carb-loading-fueling-tandem/74950/5 "2025-12-03T20:36:01Z")
@meghan_finley4 How was the marathon? Looked like you had beautiful weather. It’d be awesome if you shared what worked for managing diabetes during the run or even if you had to put something on the “not trying that again” list. I’m also curious about how the fundraising part of running for BreakthroughT1D went for you.