Fueling for a half marathon starts days before the race and continues through the finish line. The core strategy is straightforward: build up your carbohydrate stores in the days before, eat a reliable breakfast on race morning, take in 30 to 60 grams of carbs per hour during the run, and refuel with a mix of carbs and protein afterward. The details of each phase matter, though, and getting them right can mean the difference between a strong final few miles and a miserable bonk.
The Week Before: Taper Nutrition
As you reduce your training volume in the final week, your instinct might be to eat less too. Resist that. Your body is using the taper period to repair accumulated muscle damage and build up energy reserves. Cutting calories during this window forces your body to prioritize basic functions over repair and recovery, undermining the whole point of tapering.
During the early part of taper week, aim for about 5 to 7 grams of carbohydrates per kilogram of body weight per day. For a 70-kilogram (154-pound) runner, that’s roughly 350 to 490 grams of carbs daily. This is a slight step down from peak training weeks but still enough to keep your muscles well supplied. Think rice, pasta, oatmeal, bread, potatoes, and fruit as your staples.
Carb Loading: 36 to 48 Hours Out
In the final 36 to 48 hours before race day, bump your carb intake up to 10 to 12 grams per kilogram per day. For that same 70-kilogram runner, that means 700 to 840 grams of carbohydrates spread across the day. That’s a lot of food, and it should feel like a lot. You’re not just eating normally with extra pasta at dinner. You’re deliberately stuffing your muscles with glycogen, the stored fuel they’ll burn during the race.
This is where many runners fall short. They eat “a big bowl of pasta” the night before and call it carb loading, when the real protocol calls for sustained high-carb eating across two full days. Spread it out: large portions at meals, plus carb-rich snacks like bagels, pretzels, juice, and dried fruit between meals. Keep fat and fiber relatively low during this phase so you don’t end up bloated or dealing with digestive trouble on race morning.
Race Morning Breakfast
Eat your pre-race meal 2 to 3 hours before the gun goes off. This gives your body enough time to digest and move food out of your stomach. The meal should be high in carbohydrates, moderate in protein, and low in both fat and fiber. A classic option is a plain bagel with a thin layer of peanut butter and a banana, or oatmeal with honey and a bit of fruit.
This is not the morning to experiment. Whatever you eat before race day should be something you’ve tested multiple times during training. Even foods that seem perfectly safe can cause cramping or nausea under race conditions if your body isn’t used to processing them before hard effort.
Fueling During the Race
For a half marathon, you should aim for 30 to 60 grams of carbohydrates per hour, starting around the 45-minute mark. Your muscles have enough stored glycogen to power roughly 90 minutes of hard running, so if you’re finishing in under 90 minutes, you can get away with minimal fueling. For most runners finishing between 1:45 and 2:30, though, mid-race fuel makes a real difference in the final miles.
Most energy gels contain 20 to 25 grams of carbs per packet, so taking one every 30 to 45 minutes puts you right in the target range. Sports drinks count toward your carb intake too, typically providing 14 to 20 grams per 8-ounce serving. You can mix gels and sports drinks, but be aware that doubling up concentrates a lot of sugar in your stomach at once, which can cause cramping.
Liquid and gel-based fuels work better during running than solid food. Running jostles your stomach, and solid foods like bars or fruit take significantly longer to break down and convert to usable energy. Liquids empty from the stomach faster and cause less GI distress at higher intensities. Save the real food for easy training runs if you prefer it.
Choosing Your Carb Sources
If you’re taking in more than 60 grams of carbs per hour, using a single sugar source (glucose alone, for example) is likely to cause stomach problems. Products that combine two types of sugar, like glucose with fructose or maltodextrin with fructose, use different absorption pathways in your intestine, allowing your body to process more total carbohydrate with fewer issues. For most half marathon runners staying in the 30 to 60 gram range, this is less critical, but it’s worth knowing if you’re a heavier runner or plan to push the upper end of that intake.
Hydration and Sodium
There’s no single fluid intake number that works for everyone because sweat rates vary widely based on body size, fitness, humidity, and temperature. The best approach is to calculate your own sweat rate before race day: weigh yourself before and after a training run (without clothes), add back the weight of any fluid you drank during the run, and divide by the hours you ran. The result tells you how much fluid you lose per hour.
Along with water, you need sodium. The recommendation for endurance exercise is 300 to 600 milligrams of sodium per hour. Most sports drinks contain some sodium, but often not enough for heavy sweaters or hot conditions. Electrolyte tablets, salt capsules, or higher-sodium drink mixes can fill the gap. Drinking too much plain water without sodium, especially on a warm day, raises the risk of a dangerous condition where your blood sodium levels drop too low.
Train Your Gut Before Race Day
Your digestive system adapts to what you ask it to do, and this is one of the most underappreciated parts of race fueling. Runners who practice eating and drinking during training runs experience significantly better stomach comfort over time. Your gut literally becomes more efficient at absorbing carbohydrates when you train it regularly.
A high-carbohydrate diet over as little as two weeks can roughly double the number of glucose transporters in your intestinal lining, meaning your body can absorb and use more of the fuel you take in during the race. In one study, cyclists who supplemented with extra carbohydrates during training for 28 days showed measurably improved carbohydrate absorption during exercise. The practical takeaway: start practicing your race fueling plan during long runs at least 4 to 6 weeks before the race. Use the same products, the same timing, and the same quantities you plan to use on race day.
If you currently don’t eat anything during runs and plan to start, begin with small amounts and build up gradually. Even something as simple as a few sips of sports drink every 20 minutes gives your gut a training stimulus.
Caffeine as a Performance Tool
Caffeine is one of the most well-supported performance aids for endurance running. A dose of 3 to 6 milligrams per kilogram of body weight, taken about an hour before the race, has been shown to improve endurance performance by 2 to 7 percent. For a 70-kilogram runner, that translates to roughly 200 to 400 milligrams, or about two to four cups of coffee.
More isn’t better here. Doses above 6 milligrams per kilogram don’t reliably add further benefit and increase the risk of jitteriness, a racing heart, and GI distress. If you don’t regularly consume caffeine, start with the lower end of the range and test it during a training run first. Caffeinated gels are another option for a mid-race boost, but factor their caffeine content into your total so you don’t overshoot.
Recovery Fueling After the Finish
What you eat in the first 30 minutes after finishing matters more than you might expect. Your muscles are primed to absorb and store carbohydrates at a much higher rate immediately post-exercise. Waiting just two hours cuts the rate of glycogen replenishment in half.
The target is a combination of carbohydrates and protein at a ratio of about 3 to 1 or 4 to 1. A chocolate milk, a smoothie with fruit and protein powder, or a bagel with turkey and juice all hit this ratio reasonably well. The carbs replenish your glycogen stores, and the protein kickstarts muscle repair. You don’t need to obsess over exact grams in the moment. Just get something in your stomach quickly, prioritize carbs, and include a moderate portion of protein.
In the hours that follow, continue eating carb-rich meals. Your body stays in an elevated state of glycogen rebuilding for the rest of the day, so this isn’t the time for a low-carb approach. A proper recovery meal within two to three hours, followed by normal eating through the rest of the day, sets you up to bounce back faster in the days ahead.