In this part of our series on endurance fueling with T1D, Riccardo Raso moves from pre-race preparation into race execution. The focus shifts from building availability to managing delivery — how fueling, hydration, sodium, and caffeine are adjusted across bike and run to balance performance with glucose and gut stability in a Type 1 diabetes context.
As before, the guiding principle is doing what is repeatable, predictable, and defensible under race stress.
The Full Series:
- The T1D Athlete Mindset
- Carb Loading with T1D
- Triathlon Fuel & Hydration Plan (this article)
- Glucose Monitoring during Training and Races
- Fuel Adjustments Based on Glucose Levels
Hydration Plan
My goal is to start euhydrated without overdrinking. A widely used reference is ~5–10 mL/kg in the last 2–4 hours before exercise (so, for 74 kg: ~370–740 mL total), adjusted to urine output and conditions.1
I operationalize this with water + Zero Drink electrolyte tablets. Two practical dilutions I use (to match climate and sweat loss), keeping broadly aligned with guidance that sodium in fluids can help with thirst/fluid retention and is often discussed in the ~20–50 mmol/L range depending on needs:2
- Mild/cool conditions: 1 tablet in 750 mL (≈400 mg sodium/L; lighter taste, adequate if sweat loss is low).
- Hot/humid or heavy sweating: 1 tablet in 500–600 mL (≈600–500 mg sodium/L; closer to the lower end of the “sodium-supportive” range), or 2 tablets in 750 mL when I need a stronger sodium hit.
Pre-start, this is enough to support fluid retention without turning the pre-start window into a GI or bathroom problem. (For context, ACSM’s broader fluid replacement guidance emphasizes starting euhydrated and replacing electrolytes appropriately.3
During the bike, I can push sodium concentration higher because sweat loss dominates and intake execution is easier.
Pre-Swim Gels: Why I Usually Skip Them
Many triathletes take a gel immediately before the swim, but I generally do not. With T1D, my glucose is typically stable, glycogen stores are already full, and the adrenergic “start-line” response can increase blood glucose via catecholamine-driven hepatic glucose output; adding a gel at this point can easily destabilize an otherwise well-controlled start.4
The role of epinephrine and norepinephrine in increasing hepatic glucose production around exercise is well described in the literature5
, and competition-related stress has also been reported as a driver of transient hyperglycemia in athletes with T1D.6
If I do feel the need for a safety top-off (for example, a downward CGM trend during prolonged call-ups), I use Nrgy Gel 22.5 (or similar electrolyte-free product). Practically, I keep this as an emergency option until the very last minutes and simply hand it to a spectator if it turns out not to be needed.
Last but not least, my swim duration is consistently under 59 minutes, even in adverse conditions on the longer full-distance Ironman (3.8km). For this reason, I do not see a physiological need (glycogen stocks are full already) for additional carbohydrate immediately before the swim, as I begin structured fueling as soon as I transition onto the bike.
Bike vs Run: Two Different Fueling Mindsets
On the bike, I can tolerate higher and more consistent carbohydrate intake because mechanical stress and gut impact are lower, and fueling is easier to execute precisely. So the approach is closer to “execute the plan + adjust early based on trend.”
On the run, I’m more conservative: intake is slightly reduced and spacing becomes more important as impact, heat, and GI sensitivity increase. The mindset shifts from “maximize intake” on the bike to “protect glucose and gut stability” on the run—still using trend arrows, but with fewer aggressive moves.
Note: Riccardo fuels with 130-140 g/h. Read how he reached this number.
Fueling the Bike Segment
(90 km distance; very hot & humid conditions)
Expected Duration (Based on Actual Bike Speed)
- Best case (~42.5 km/h): ~2 h 07
- Typical case (~40 km/h): ~2 h 15
- Worst case (climbing/disrupted pacing): ~2 h 45 (≈ +30 min)
Bottles carried
- 2 × 1 L bottles
- 1 × 750 mL bottle
Electrolytes
- Each 1 L bottle: ~1000 mg sodium
- 750 mL bottle: ~250 mg sodium
Carbohydrates: Planned Intake
- Each 1 L bottle = 120 g CHO
- 750 mL bottle = 0 g CHO
- 2 × Gels 40 (no electrolytes; 1 caffeinated, 1 non-caffeinated) ≈ 80 g CHO
(Note: Riccardo has since switched to using Nrgy Gels, which have 22.5 or 45 g CHO each, so his current plan is slightly different)
Bike Totals (Base Plan)
- Fluids: 2.75 L
- Carbohydrates: 320 g CHO
- Sodium: 2250 mg
What This Delivers Per Hour
- ~2 h 07: ~151 g CHO/h | ~1063 mg sodium/h | ~1.30 L/h
- ~2 h 15: ~142 g CHO/h | ~1000 mg sodium/h | ~1.22 L/h
- ~2 h 45: ~116 g CHO/h | ~818 mg sodium/h | ~1.00 L/h
Because my real bike target is ~120 g/h on the low end, ~160 g/h on the high end, and ~140 g/h as a typical average, I use one simple rule:
If the bike stretches to ~2 h 45, I carry one additional gel (40–45 g CHO).
- Revised total: 360 g CHO
- At ~2 h 45 → ~131 g CHO/h, back into my normal “average” range for long, hard conditions.
Practical Execution on the Bike
My priority on the bike is to drink as much as possible — it’s the easiest segment to take fluids reliably.
The 750 mL bottle is a functional tool to:
- Top up fluids when needed, and
- Hold back water for cooling if heat stress rises.
If I’m still thirsty or heat-stressed, I grab additional water at the final aid stations without changing the core plan. The other aid stations also work as insurance if anything goes wrong (e.g. dropping gels — which hasn’t happened so far).
Full Ironman Note (90 km Mark)
In a full Ironman, I keep an identical copy of this bike fueling/hydration setup in my special needs bag at km 90, so the second half of the bike follows the same philosophy and structure.
Fueling the Run Segment
(Half-marathon distance; very hot & humid conditions)
Carbohydrates
- ~22.5–30 g CHO every 15 minutes (≈ 90–120 g CHO/hour)
Sodium
- ~190–240 mg sodium every 15 minutes (≈ 760–960 mg sodium/hour)
Fluids & Cooling
- Water at every aid station (excluding the last two)
- External cooling whenever possible:
- Water over head/torso
- Sponges
- Self-cooling with bottles
Caffeine Strategy during Run (Half Marathon Length)
I take ~200 mg caffeine paired with ~35–40 g CHO toward minute 50 of the first hour — practically ~45–55 minutes into the run.
This timing tends to be a better trade-off than taking caffeine very early. Together with higher carbohydrate intake and higher intensity versus the marathon, it supports the second half of the run when fatigue and heat load accumulate, without front-loading stimulation.
Marathon (for reference)
- Gel with ~200 mg caffeine at ~km 12
- Gel with ~200 mg caffeine at ~km 30
Everything else in the run plan remains identical: fuel every 15 minutes, keep sodium explicit, drink at every station, cool aggressively.
I’m conscious that very high caffeine loads can increase cramp susceptibility in some individuals, so I keep caffeine as a race-day tool used with intent, especially in heat — not something used casually.7
Why This Structure Works for Me
Across the whole plan, my priority is repeatability and predictability: high carbohydrate availability (including very high intakes now shown to be practically tolerable with glucose + fructose systems in trained athletes8), while keeping T1D stability protected by timing (2.5 h buffer), conservative fat and fiber on race morning, and avoiding “pre-swim chaos” that isn’t physiologically necessary.
Up next: In the next part of this series, Riccardo breaks down how he monitors blood glucose during a race — including CGM trends, decision-making in real time, and how he responds when numbers start to drift. Read it here.