A 70.3 sits in a complicated nutritional space. The intensity is higher than a full Ironman, which means your gut is under more stress. The duration is shorter, which means you have fewer hours to accumulate fuel. Miss your targets and the run falls apart — typically around miles 6–9 where under-fueled athletes hit their personal wall.

This guide gives you the exact carb, fluid, and sodium targets for a 70.3, with a specific hour-by-hour schedule for three common finish times: 4:30, 5:30, and 6:30.

Why 70.3 fueling is different from full Ironman

The full Ironman allows a longer fueling window at lower intensity. You have 5–7 hours on the bike to steadily accumulate carbohydrate, and your pace is aerobic enough that gut blood flow is relatively protected. A 70.3 is different in two critical ways:

  • Higher intensity: 70.3 bike effort sits 10–15% higher than Ironman bike effort for most athletes. Higher intensity means more gut vasoconstriction, which means lower carbohydrate absorption capacity per hour.
  • Shorter window: You have 2.5–4 hours on the bike versus 5–7 hours in a full Ironman. Every hour matters. Miss a fueling window on the bike and there is less time to compensate.

The practical result: you need to start fueling earlier, be more consistent, and keep carbohydrate concentration moderate to protect absorption.

Carb targets: bike and run

  • Bike: 60–75 g of carbohydrate per hour. If you have trained your gut with mixed sources (glucose plus fructose at 2:1), you can push toward 75–90 g/hr. If you use single-source products, stay at 60 g/hr.
  • Run: 40–60 g of carbohydrate per hour. Gut tolerance drops sharply on the run after 2.5–4 hours of biking. Stay on the lower end if your stomach is borderline.

Fluid targets

Target 500–700 ml per hour across both the bike and run legs. In heat above 25°C, push toward 700–900 ml per hour and increase sodium intake proportionally. Never drink plain water in large volumes without electrolytes on a multi-hour effort.

Sodium targets

500–800 mg of sodium per hour throughout the race. Salty sweaters and athletes racing in heat should target the upper end. Sodium keeps plasma volume up, reduces cramping, and protects against hyponatremia if fluid intake is high.

Hour-by-hour schedule: 4:30 finisher

Approximate splits: 25-min swim, 2:25 bike, 10-min transitions, 1:50 run.

  • T1 / first 10 min on bike: 1 gel with sodium (22–27g carbs), first sips of electrolyte bottle.
  • Bike hour 1 (0:00–1:00): 2–3 gels or chews (~60g carbs), 500–600ml electrolyte drink (~300mg sodium).
  • Bike hour 2 (1:00–2:00): 2–3 gels or chews (~60g carbs), 500–600ml, 1 caffeinated gel in this window (25–50mg caffeine).
  • Bike final 25 min (2:00–2:25): 1 gel, 200–300ml fluid, reduce intake 15 min before T2.
  • T2: 1 gel immediately entering transition.
  • Run hour 1 (0:00–1:00): 2 gels (~50g carbs), water at every aid station.
  • Run final 50 min (1:00–1:50): 1–2 gels, flat cola from aid stations from mile 6 onward.

Hour-by-hour schedule: 5:30 finisher

Approximate splits: 35-min swim, 2:55 bike, 12-min transitions, 2:08 run.

  • T1 / first 10 min on bike: 1 gel with sodium, begin electrolyte bottle.
  • Bike hour 1: 2–3 gels (~60–65g carbs), 600ml electrolyte drink.
  • Bike hour 2: 2–3 gels (~60g carbs), 600ml, 1 caffeinated gel.
  • Bike hour 3 (first 55 min): 2 gels (~50g carbs), 400–500ml, reduce 15 min before T2.
  • T2: 1 gel immediately.
  • Run hour 1: 2 gels (~50g carbs), water at every station, cola from mile 5.
  • Run hour 2 (final 68 min): 2 gels, cola and water at stations, 1 caffeinated gel at mile 10.

Hour-by-hour schedule: 6:30 finisher

Approximate splits: 45-min swim, 3:30 bike, 15-min transitions, 2:30 run.

  • T1 / first 10 min on bike: 1 gel, begin electrolyte bottle.
  • Bike hours 1–2: 2–3 gels per hour (~60g carbs/hr), 600–700ml per hour, caffeinated gel in hour 2.
  • Bike hour 3: 2 gels (~50g carbs), 500ml, consider real food (banana, rice cake) if gut allows.
  • Final 30 min on bike: 1 gel, reduce solid food, keep fluids up.
  • T2: 1 gel immediately, water.
  • Run hours 1–2.5: 1–2 gels per hour (40–50g carbs), water at all stations, cola from mile 6 onward, electrolyte tabs every hour.

T1 fueling protocol

Your first calories of the race should come in T1 or within the first 5 minutes on the bike. The swim burns relatively little but the adrenaline and water temperature suppress appetite for 15–30 minutes afterward. Do not wait until you feel hungry. Get one gel with sodium in immediately as you leave transition. This starts the fueling clock before appetite suppression kicks in.

T2 fueling protocol

Take one gel as you enter T2, before you start changing shoes. The transition gap — typically 5–12 minutes of no intake — is a fueling dead zone. The T2 gel bridges it. Running the first mile of a half marathon already 10–15 minutes behind on carbohydrate intake is one of the most common 70.3 run-leg mistakes.

What to put in transition bags

  • T1 bag: 1 gel taped to bike helmet or top tube. 2 electrolyte bottles pre-loaded on bike (one mixed, one plain water for dilution). Electrolyte tabs in a small ziplock on the bike frame.
  • T2 bag: 4–6 gels in jersey pocket or race belt. 1 caffeinated gel marked separately for mile 8–10. Small salt capsules if you sweat heavily.

Common 70.3 fueling mistakes

  • Waiting to feel hungry: Hunger lags energy deficit by 20–30 minutes. Eat on a schedule, not on sensation.
  • Skipping T2 gel: Running the first mile in a caloric hole you created yourself. Take the gel before you leave transition.
  • Racing the bike at Ironman targets: 70.3 bike intensity is higher — your gut can handle slightly less per hour. Stay at 60–70g carbs/hr unless you have specifically trained at higher volumes.
  • Using race-provided products untrained: Check the race nutrition sponsor in advance. If you have not trained with their gels, carry your own.
  • Skipping sodium: Hyponatremia risk is lower than full Ironman but still real. 500–800 mg sodium per hour keeps plasma volume stable.

Frequently asked questions

How many gels do I need for a 70.3? Approximately 8–14 gels depending on your finish time and carbohydrate sources. A 5:30 finisher taking 60g/hr of carbohydrate from gels alone would need roughly 10–12 gels across the bike and run. Most athletes supplement with sports drink on the bike, which reduces the gel count by 3–5.

Should I eat solid food during a 70.3? Solid food (banana, rice cake, bar) is an option in the first 30–40 miles of the bike when intensity is controlled and gut blood flow is higher. Most athletes shift to liquid and gel nutrition in the final third of the bike and the entire run. If you are a 6:30+ finisher, real food on the bike can help with palatability fatigue.

How much water should I drink during a 70.3? 500–700 ml per hour in normal conditions (15–22°C). In heat above 25°C, push toward 700–900 ml per hour. Always pair increased water intake with increased sodium to prevent hyponatremia.

What should I eat the morning of a 70.3? 1–2 g of carbohydrate per kg bodyweight, 2–3 hours before your wave start. White toast with jam, banana, and a small coffee is a reliable combination. Nothing high in fat, fiber, or protein. Nothing new.

How do I carry nutrition on the 70.3 bike? Two aero bottles between the aerobars for easy sipping. A top-tube bag for gels and chews. A behind-the-saddle pouch for backup nutrition and electrolyte tabs. Tape one gel directly to the stem for your T1 first feed.