How many carbohydrates do you need for a half marathon?
A half marathon takes between 90 minutes and 3+ hours depending on your pace. Below 90 minutes, most runners can complete the race on stored glycogen alone — no mid-race fuelling required. Above 90 minutes, your glycogen stores may run low in the final 5 km, which is where runners who haven't fuelled start to slow dramatically.
In the two days before your race, increase carbohydrate intake to around 7–10 grams per kg of body weight per day. This isn't a special 'carb-loading protocol' — it simply means eating more pasta, rice, bread, and potatoes than usual while reducing high-fat and high-fibre foods that can cause stomach issues.
Don't try anything new in race week. The foods that work for you in training are the foods that should be on the plate before your race.
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What to eat the morning of the race
Eat 2–3 hours before the start. The goal is a meal that tops up liver glycogen after overnight fasting without causing stomach discomfort during the race. A good race-morning meal is high in easily digestible carbohydrates, moderate in protein, and low in fat and fibre.
Oats with honey, white toast with peanut butter, or a banana with a sports drink all work well for most runners. Avoid high-fibre cereals, full English breakfasts, or anything you haven't tested before a training long run.
If the race starts very early and eating 2–3 hours before isn't practical, eat something smaller — even a banana and some sports drink — as close to 90 minutes before the start as your stomach allows.
- →2–3 hours before: 80–100g carbohydrates (oats, white toast, bagel, banana + sports drink)
- →60–90 min before: sip water or electrolyte drink, avoid high-sugar gels to prevent an insulin spike
- →15 min before: optional 25g carb gel or banana if you feel your energy is low
Fuelling during the race
If your target time is under 1:30, you can almost certainly complete the race without mid-race fuel. If your target is 1:30–2:00, one gel around 45–60 minutes in is worth considering. If you're targeting 2:00 or slower, plan to take on fuel every 45–60 minutes.
Gels, chews, and sports drinks are all valid options. The only rule is that you must have practised with whichever product you plan to use — race day is not the time to discover your stomach doesn't tolerate a particular gel brand.
Take gels with water, not sports drink — combining the two can deliver too much sugar too quickly and cause stomach cramping.
Hydration strategy
Drink to thirst, not to a schedule. Overhydration during a half marathon is a real risk — hyponatremia (dangerously low sodium from drinking too much plain water) is more common in race settings than dehydration.
In temperate conditions, most runners need 400–600 ml per hour. In hot conditions, aim for 500–800 ml per hour. Add electrolytes (from sports drinks, tabs, or gels) if you're sweating heavily or running in heat.
Don't skip every aid station, but don't feel obligated to drink at all of them either. A small sip at each station is often the most practical approach.
Recovery nutrition after the race
The 30–60 minutes after finishing are the most important window for recovery nutrition. Your muscles are most receptive to glycogen replenishment in this window, and delaying eating significantly extends the time until you feel normal again.
Aim for a meal or snack with 3:1 carbohydrate to protein ratio — chocolate milk, a recovery shake, or a meal of rice and chicken all work. Avoid alcohol for at least 2–3 hours post-race; it significantly impairs muscle repair.
Over the following 24 hours, prioritise protein (1.6–2.0g per kg body weight) and stay well-hydrated. Don't restrict food after a race — your body has work to do.