The short answer
Half-marathon fueling should be based on time on course, conditions, tolerance, and what you have practised. A runner expecting to finish near 75 minutes has a different problem from someone expecting more than two and a half hours.
Use the table below as a rehearsal starting point, not a prescription. World Athletics' distance-running guidance supports personalised carbohydrate and fluid plans and notes that even shorter long-distance events may benefit from carbohydrate exposure, while the practical value of eating during the race increases as duration rises.1, 2
Pick a starting lane
| Expected finish time | Evidence-based context | Practical rehearsal question |
|---|---|---|
| About 60–75 minutes | Small amounts or carbohydrate mouth exposure can be useful in high-intensity exercise; a full gel schedule may be unnecessary | Can a familiar pre-race meal and small tested amount meet the event demands? |
| About 75–150 minutes | General endurance guidance commonly uses 30–60 g carbohydrate per hour | What amount within or toward that range is tolerable at your effort? |
| Beyond about 150–180 minutes | Guidance allows up to 90 g/h for prolonged endurance exercise, usually using mixed carbohydrate sources | Is a higher intake useful and already well practised, or is a lower familiar intake the better starting point? |
These ranges come from broader endurance guidance, not a trial assigning a gel count to every half-marathon finish time.2, 8 The overlap around 60–75 minutes and 2.5–3 hours reflects context rather than a switch that occurs at a specific minute. Do not jump to 90 g/h because the predicted finish exceeds 2.5 hours.
The boundaries are intentionally fuzzy. A hot, humid race, an athlete with diabetes, a history of gastrointestinal symptoms, or a very aggressive pace changes the decision.
Turn the hourly range into a race total
Worked example: two hours at a rehearsed 40 g/h means 80 g during the race. Three 25 g gels provide 75 g, or 37.5 g/h over two hours. If a familiar drink supplies another 20 g, the total becomes 95 g, or 47.5 g/h. Count all sources before adding another gel. These numbers illustrate arithmetic, not a prescription to consume every item.
Breakfast supports the starting state; do not subtract its entire carbohydrate content from the planned during-race total. Read actual labels and put each tested dose near a feasible course opportunity. Fuel timing and fluid access still need rehearsal.
Build the plan in four rehearsals
Rehearsal 1: establish the baseline
Use a familiar pre-run meal and take only the fuel you already tolerate. Record start time, duration, conditions, products, carbohydrate estimate, fluid, energy, and stomach comfort.
Rehearsal 2: add one deliberate dose
Keep the route and pre-run meal similar. Add one small carbohydrate dose at a planned time. Do not simultaneously change caffeine, product type, breakfast, and pace.
Rehearsal 3: copy the race opportunity
If the event has aid stations, practise taking fuel and fluid at similar intervals. If you will carry fuel, test the exact pocket, belt, or flask setup.
Rehearsal 4: run the complete script
Use race shoes, breakfast timing, products, carrying system, and the intended first-fuel cue. Finish with enough control to judge the plan; this is a rehearsal, not a race.
A simple fueling card
Write this before the start:
- expected finish range;
- breakfast time and familiar foods;
- first fuel cue;
- later fuel cues;
- where water is available;
- one backup if the stomach feels unsettled;
- one stop rule for concerning symptoms.
The card prevents late-race bargaining. It also exposes impossible plans—for example, scheduling three gels when you can only carry two and the course does not supply your product.
Fluid is not a fixed number
Sweat rate varies with weather, pace, clothing, body size, acclimation, and the individual.3 Do not copy another runner's litres-per-hour target or try to replace every gram of body-mass change during the race. Excess drinking can also be dangerous.
Use the sweat-rate hydration worksheet in race-like training, then treat the result as context rather than a command. Avoid drinking deliberately beyond thirst or an individually assessed plan. Gaining weight while forcing fluid is a warning sign of overdrinking, not a target; weight alone cannot diagnose hydration or sodium status.
When the plan fails in training
If nausea, bloating, or sloshing appears:
- Check whether pace was harder than planned.
- Reduce dose size before abandoning carbohydrate entirely.
- Check product concentration and whether fluid was available.
- Remove one variable at the next rehearsal.
- Seek qualified sports-nutrition or medical help if symptoms are severe or repeat despite conservative changes.
Carbohydrate intake during endurance exercise improves performance on average, but the effect and tolerable dose vary.4 The useful plan is the one you can execute safely—not the largest number on a label.
Compare rehearsals with the same four numbers
After each rehearsal, record carbohydrate consumed, fluid consumed, stomach comfort from 0–10, and pace change in the final third. Add one sentence about conditions. The point is not to create a perfect laboratory; it is to notice whether a change helped under comparable circumstances.
Do not promote a plan after one lucky run. Look for two or three similar sessions with stable comfort and late-run control. If heat or humidity changes sharply, treat that as a new condition rather than proof the earlier plan failed. Fluid guidance recommends individualisation because sweat losses and electrolyte needs vary.5 Hyponatraemia guidance also makes clear that more drinking is not automatically safer.6
This evidence does not tell you which gel brand, flavour, or exact schedule will work. World Athletics and AIS resources emphasise a personalised, food-first approach and practice inside the athlete's real environment.7, 8
Safety boundary
This guide is educational and not medical advice or individual nutrition advice. Diabetes, kidney or heart conditions, pregnancy, a history of eating disorder or low energy availability, recurrent fainting, or medication affecting fluid balance needs professional guidance. Stop and seek urgent help for confusion, collapse, chest pain, severe breathing difficulty, or other acute symptoms.
26weeks.ai keeps the half-marathon goal and weekly work together when life changes. It cannot replace a clinician or sports dietitian, but it can reduce the training-plan decisions around the race. Start training now.
Sources and evidence limits
Sources and associated claims reviewed October 17, 2026. Practical examples are editorial guidance, not individually validated prescriptions.
1 World Athletics. Nutrition for Athletics consensus materials. (Official health and science library)
2 Burke LM et al. Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers. (2019). Read the source.
3 Gatorade Sports Science Institute. Fluid Loss Calculator and sweat-rate method. (Calculator)
4 Ramos-Campo DJ et al. The ergogenic effects of acute carbohydrate feeding on endurance performance: a systematic review, meta-analysis and meta-regression. (2024). Read the source.
5 American College of Sports Medicine et al. American College of Sports Medicine position stand. Exercise and fluid replacement. (2007). Read the source.
6 Hew-Butler T et al. Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. (2015). Read the source.
7 World Athletics. Nutrition for Athletics consensus statement. (Official PDF)
8 Australian Institute of Sport. Sports drinks: carbohydrate guidance by exercise duration. (Official guidance)