Race-day fuelling and hydration
How much carbohydrate, fluid and sodium a race actually needs — set against how long you will be out there and what the weather is doing. Built around Indian conditions, where the humidity does more damage than the temperature.
Enter your weight and how long you expect to be running.
Measure your own sweat rate
Every hydration guideline in the world is a population average. Twenty minutes of arithmetic after one long run replaces it with your own number, and in Indian conditions the spread between runners is enormous — from under half a litre an hour to well over two.
Weigh yourself before and after a run, in light clothing, towelled dry.
Carbohydrate by time on your feet
Rendered on the server. The only variable that decides carbohydrate need is duration — not distance, and not your weight.
| Time on feet | Carbs per hour | Total for the race | Roughly equivalent to |
|---|---|---|---|
| 45 min | none needed | water only | — |
| 1 hr | 30–60 g | 30–60 g | 1–2 gels, or the same in sports drink, dates or banana |
| 1.5 hr | 30–60 g | 45–90 g | 2–4 gels, or the same in sports drink, dates or banana |
| 2 hr | 30–60 g | 60–120 g | 2–5 gels, or the same in sports drink, dates or banana |
| 2.5 hr | 60–90 g | 150–225 g | 6–9 gels, or the same in sports drink, dates or banana |
| 3 hr | 60–90 g | 180–270 g | 7–11 gels, or the same in sports drink, dates or banana |
| 3.5 hr | 60–90 g | 210–315 g | 8–13 gels, or the same in sports drink, dates or banana |
| 4 hr | 60–90 g | 240–360 g | 10–14 gels, or the same in sports drink, dates or banana |
| 4.5 hr | 60–90 g | 270–405 g | 11–16 gels, or the same in sports drink, dates or banana |
| 5 hr | 60–90 g | 300–450 g | 12–18 gels, or the same in sports drink, dates or banana |
| 5.5 hr | 60–90 g | 330–495 g | 13–20 gels, or the same in sports drink, dates or banana |
| 6 hr | 60–90 g | 360–540 g | 14–22 gels, or the same in sports drink, dates or banana |
A standard energy gel carries about 22–25 g of carbohydrate; 500 ml of a typical sports drink about 30 g; one medium banana about 25 g; four dates about 25 g. Above roughly 60 g an hour you need a glucose-and-fructose mixture rather than a single sugar, because a single transporter in the gut saturates around that point.
Fluid and sodium by conditions
| Conditions | Fluid per hour | Sodium per litre | What it looks like |
|---|---|---|---|
| Cool & dry (under 18°C) | 400–600 ml | 300–500 mg | One cup at most aid stations |
| Warm (18–26°C) | 500–750 ml | 400–700 mg | Two cups at most aid stations, or a soft flask refilled |
| Hot & humid (over 26°C) | 600–900 ml | 500–800 mg | Drink at every station, plus what you carry — and pour water over your head as well as into it |
Do not out-drink your sweat rate. Exercise-associated hyponatraemia — dangerously diluted blood sodium from drinking more fluid than you lose — is far less common than dehydration but far more dangerous, and it happens disproportionately to slower runners in hot races who drink at every station on principle. If you finish a race heavier than you started it, you drank too much. Use your measured sweat rate as the ceiling, not the floor.
What is different about fuelling an Indian race
Two things, and both push in the same direction.
Humidity, not heat, is the limiter. Sweat cools you only when it evaporates. In Mumbai in January or Hyderabad in August, the air is already close to saturated, so sweat runs off you without cooling you — you pay the fluid cost of thermoregulation without getting the benefit. This is why runners visiting from cooler climates are so consistently caught out by a January start in a city that is only 24°C. Plan fluid for the humidity, not the thermometer.
Start times are early, so breakfast is early. A 05:40 gun means eating at around 03:30, which almost nobody does naturally. Practise it: a small, tested, mostly-carbohydrate meal at the actual hour, on at least two long runs before race day. Discovering at 04:00 on race morning that you cannot face poha is a bad time to find out.
Practise everything, change nothing
The single most reliable rule in race nutrition is that race day contains no experiments. Every gel, drink, date and biscuit you plan to use should have been through your gut at race pace at least twice in training. Aid stations at Indian races serve what they serve; if you need something specific, carry it.
If you want the calorie side of the Indian food that surrounds all of this — what a plate of poha or two idlis actually delivers — the sister site ThaliFacts publishes it by real Indian serving sizes rather than per 100 g.
Questions
How many carbs do I need during a marathon?
For a race lasting over two and a half hours, published sports-nutrition guidance is 60 to 90 grams of carbohydrate an hour, and reaching the upper end requires a mix of glucose and fructose because the gut can only absorb so much of any single sugar. For a race of one to two and a half hours, 30 to 60 grams an hour is sufficient.
How much should I drink during a race in India?
In the heat and humidity of most Indian races, 600 to 900 ml an hour is a reasonable planning range — but the honest answer is that it depends on your own sweat rate, which you can measure in one training run using the calculator on this page. Do not drink more than you sweat: over-drinking causes hyponatraemia, which is rarer than dehydration but considerably more dangerous.
Do I need electrolytes or is water enough?
For anything under about an hour, water is enough. Beyond that, and especially in Indian heat where sweat losses are large, sodium matters — roughly 300 to 800 mg per litre of fluid depending on conditions and how salty a sweater you are. If you finish long runs with salt crusted on your face, you are at the high end.
What should I eat before an Indian race morning?
Something you have already tested on several long runs, eaten two to three hours before the start, and mostly carbohydrate with little fat or fibre. Poha, upma, idli with a little jaggery, toast with jam or a banana all work. Race morning is not the day to try a new breakfast, and it is certainly not the day to try a heavy one.
How do I measure my sweat rate?
Weigh yourself naked before a run, run for a known time without stopping to eat or use the toilet, note how much you drank, then towel dry and weigh again. Every kilogram of body mass lost is roughly a litre of sweat. Add back what you drank and divide by the hours.
Every time, pace and physiological figure on this site is computed from a published formula, and the formula is named and shown on the method page. Nothing here is predicted by a model you cannot check. Race details change — always confirm dates, routes and entry with the official organiser. Training guidance is general information, not individual coaching or medical advice.