The question of how many gels to consume in a marathon is one of the most empirically tractable questions in race-day nutrition. The published evidence gives a defensible range, the underlying physiology is well-understood, and the variation between runners is meaningful but bounded. This piece sets out the answer, the reasoning, and the practical considerations for an Indian marathon - the Tata Mumbai Marathon, the Vedanta Delhi Half, the IDBI New Delhi Marathon, and the wider calendar - where heat, humidity, and product availability add variables that temperate-climate guides ignore.
The argument proceeds in five parts: what the research recommends, how to translate that to gels, how to plan the timing, what to do when things go wrong, and the Indian-context considerations.
What the research says about carbohydrate intake during a marathon
The current consensus emerges from work by Asker Jeukendrup and colleagues, published across the 2000s and 2010s in journals including Sports Medicine and the European Journal of Sport Science.
The carbohydrate-per-hour target
For exercise lasting 2.5-3 hours or longer, the recommended carbohydrate intake is approximately 60-90 grams per hour. For runners using a combination of glucose and fructose (transported into the gut by different mechanisms), the upper end of this range is achievable; pure glucose intake is typically limited to 60 g/hour due to the saturation of the SGLT1 transporter.
What this delivers physiologically
Sufficient carbohydrate intake during the marathon delays muscle and liver glycogen depletion, maintains blood glucose, reduces central nervous system fatigue, and is associated with improved end-race performance. The 2014 IOC consensus statement on nutrition explicitly endorses this carbohydrate intake range for endurance events over 2.5 hours.
The lower bound for shorter races
For exercise of 1-2.5 hours, the recommended intake is lower - approximately 30-60 g/hour. For a half marathon completed in under 2 hours, 30-40 g/hour is generally sufficient. The marathon, being longer, sits in the higher range.
How many gels does that mean
Most commercial running gels deliver 22-30 g of carbohydrate per gel. The arithmetic from research to practice follows directly.
For a 3 hour 30 minute marathon
3.5 hours x 60-90 g/hour = 210-315 g of carbohydrate over the race. At 25 g per gel, that is 8-12 gels. The lower number assumes additional carbohydrate from sports drinks at on-course aid stations; the higher assumes gels are the primary fuel source. For most Indian marathons where on-course sports drinks vary in quality and consistency, planning toward the higher end of the gel count is prudent.
For a 4 hour 30 minute marathon
4.5 hours x 60-90 g/hour = 270-405 g of carbohydrate. At 25 g per gel, that is 11-16 gels. This is at the upper end of what most marathoners can comfortably consume without gut distress; many runners in this finishing range supplement with bananas, dates, or on-course solid food rather than relying entirely on gels.
For a 5 hour 30 minute marathon
5.5 hours x 60-90 g/hour = 330-495 g. At 25 g per gel, that is 13-20 gels. The published evidence on very long endurance events suggests that intake at the higher end is rarely tolerated and is not always necessary; experience suggests 12-14 gels supplemented with solid food and electrolyte drinks is the practical norm.
Timing the gels through the race
The schedule matters as much as the total.
The pre-race gel
A gel taken 10-15 minutes before the gun adds 25 g of carbohydrate to the start without significantly raising insulin (because exercise is imminent). This is supported in the IOC consensus and is widely practised. It does not count toward the in-race total; it is the bridge between breakfast and the first on-course gel.
The first hour
One gel at kilometre 8-10, approximately 45-60 minutes into the race. Earlier than this is generally not needed - liver and muscle glycogen plus the pre-race meal cover the first 60 minutes for most runners.
Subsequent gels
One gel every 25-35 minutes (or every 4-5 km at typical marathon paces) from kilometre 10 onward. The interval is chosen to keep blood glucose stable and to spread the carbohydrate load. Bunching gels together (two in 10 minutes) increases the risk of gastric distress.
The final hour
Continue the schedule. Some runners benefit from a caffeinated gel in the final 30-45 minutes, where the central nervous system effect of caffeine adds a perceived-effort reduction in the closing kilometres. See our fuel guide for the broader caffeine math.
What to do when things go wrong
The research is clear that gel tolerance varies between individuals and that race-day gut distress is the most common reason for an under-fuelled marathon.
If you cannot get a gel down
Try water with each gel (the carbohydrate concentration matters; 6-8% is the well-tolerated range, and a gel with 200 ml of water sits in this zone). Try a different brand. Use a banana or a date as a substitute - approximately 25 g of carbohydrate per medium banana, 18 g per Medjool date. Do not skip the calories entirely if you can avoid it.
If you have stomach cramps
Slow your pace. Walk through the next aid station. Take a sip of water without a gel. Resume the schedule 10-15 minutes later when the cramp settles. Continued running with severe GI distress increases the chance of stopping the race entirely.
If you forgot your gels at the start
Most Indian marathons - Tata Mumbai Marathon, Vedanta Delhi Half (the half), IDBI New Delhi Marathon - have aid stations every 2.5-5 km with water, electrolyte drinks, and on some courses bananas or biscuits. Use whatever is available. The 60-90 g/hour target is the ideal; the floor is 'do not run on empty.' Visit our Tata Mumbai Marathon page for the on-course fuel details.
Indian-context considerations
The literature on race-day nutrition is largely written for temperate climates. Indian marathons impose additional constraints.
Heat increases the carbohydrate requirement
The research on heat and exercise consistently shows that thermoregulatory load increases the energy cost of running at a given pace, primarily due to higher cardiovascular work. Heat also reduces glycogen utilisation efficiency. Practically, this means that the 60-90 g/hour target should be aimed at the upper end for races in conditions warmer than 24-25C - which describes most Indian marathons outside of the December-February window.
Gel availability and brand variation
Imported gels (GU, Maurten, SiS) are available in Indian sports shops and online (Decathlon, Amazon, marathon expo retailers) but stock can be inconsistent. Indian-made options (Fast&Up, Unived, Maverick) provide comparable carbohydrate per serving. The non-negotiable rule from the IOC consensus is to test the specific brand in long runs before race day. Race day is not the time to try a new gel.
Hydration and electrolyte balance
Indian marathon runners typically lose 1-2 litres of sweat per hour in moderate heat. The fluid intake target during the race is 400-800 ml per hour, depending on individual sweat rate and conditions. Gels alone do not cover hydration; they need to be taken with water or a low-concentration sports drink. Visit our nutrition pages for the broader fluid and electrolyte math.
Cost and budgeting
Commercial gels in India cost ₹100-180 per gel. For a marathon at the higher end of the gel count (12-14 gels including pre-race), the race-day fuel budget is approximately ₹1500-2500. This is non-trivial but predictable. Some runners use a combination of one or two premium gels for the final third of the race and lower-cost alternatives (dates, jaggery balls) for the earlier sections. Use our calculators to model your race-day fuel needs against your goal pace, our plan generator to plan your training fuelling, and visit the Running Lab for the deeper reads on endurance nutrition.