During a half marathon, you should consume 30 to 60 grams of carbohydrates per hour, starting around the 45-minute mark. That translates to roughly one energy gel or a handful of chews every 30 to 45 minutes for most runners. But race-day fueling actually starts hours before the gun goes off, and what you eat before and during the race works together to keep your energy steady across all 13.1 miles.
Your Pre-Race Breakfast
The meal you eat before the race is your fuel tank. Aim for 1 to 4 hours before the start, with the general rule being: the closer to race time, the smaller the meal. A good target is about 4.5 to 18 grams of carbohydrates per 10 pounds of body weight. For a 150-pound runner eating three hours out, that could be a couple of pieces of toast with jam and a banana, or a bowl of oatmeal with honey.
Keep this meal low in fat and fiber, both of which slow digestion and can cause stomach trouble once you start running. Foods like broccoli, cauliflower, high-fat meats, and anything greasy should be off the table. Spicy foods and alcohol are also common gut irritants on race day. A small amount of protein, around 10 to 20 grams, is fine and can help you feel satisfied without weighing you down. Think eggs on white toast rather than a loaded breakfast burrito.
Whatever you choose, this should be a meal you’ve practiced on training runs. Race morning is not the time to try something new.
When to Start Eating During the Race
Your body has enough stored glycogen to power roughly 60 to 90 minutes of hard running. For faster half marathoners finishing under 90 minutes, mid-race fueling is less critical. But if your finish time is closer to two hours or beyond, eating during the race becomes important for maintaining pace in the final miles.
Start fueling around the 45-minute mark. This gives your body time to absorb and process the carbohydrates before your glycogen stores start running low. Waiting until you feel depleted is too late, since it takes 15 to 20 minutes for ingested fuel to reach your working muscles. Many experienced runners take their first gel around mile 4 or 5, then another around mile 8 or 9, spacing intake every 30 to 45 minutes throughout the race.
Best Mid-Race Foods
Energy gels are the most popular choice because they’re compact, easy to carry, and deliver a precise dose of carbohydrates (typically 20 to 25 grams per packet). Chews and gummies work similarly and give you something to actually chew, which some runners prefer. A few runners use real food like dates, gummy bears, or small pieces of banana, though these are harder to manage at race pace.
If you’re looking at ingredient labels, products that combine two types of sugar tend to work better than those relying on a single source. Your gut absorbs glucose and fructose through separate pathways, so combining them lets you take in more total carbohydrate per hour without overwhelming your stomach. Research from Massey University found that a ratio of roughly 0.8 parts fructose to 1 part maltodextrin (a glucose source) maximized how efficiently runners burned ingested carbohydrates and improved sprint power at the end of endurance efforts by about 12% compared to water alone. Many commercial gels and drink mixes already use this dual-source formula.
Whatever you choose, wash it down with water. Taking a gel without fluid can concentrate the sugar in your stomach and trigger nausea or cramping.
Hydration and Electrolytes
Drink 16 to 24 ounces of water or a sports drink about two hours before the race. During the run, aim for 6 to 12 ounces every 20 minutes. You don’t need to hit these numbers precisely. Drinking at every aid station and adjusting based on thirst and conditions is a practical approach.
Plain water is fine for shorter efforts, but during a half marathon lasting 90 minutes or more, you also need sodium. Most runners lose enough salt through sweat to benefit from 500 to 700 milligrams of sodium per hour as a starting point. Heavy sweaters or runners racing in hot, humid conditions often need 1,000 milligrams or more per hour. If you’ve noticed white salt streaks on your hat or shirt after long runs, you’re likely a salty sweater who needs the higher end of that range.
Sports drinks provide some sodium, but often not enough on their own. Electrolyte capsules or tabs dissolved in water can fill the gap. Matching roughly 500 to 700 milligrams of sodium per 16 to 24 ounces of water works for most runners. Too little sodium over a long effort can contribute to cramping, nausea, and in extreme cases, a dangerous drop in blood sodium levels.
A Sample Fueling Plan
Here’s what a practical race-day plan looks like for a runner finishing in about two hours:
- 3 hours before: Oatmeal with banana and honey, plus 16 to 24 ounces of water
- 30 minutes before: A few sips of sports drink, possibly a small handful of pretzels
- Mile 4 to 5 (around 45 minutes): First gel with water
- Mile 8 to 9 (around 75 to 90 minutes): Second gel with water
- Every aid station: 4 to 6 ounces of water or sports drink
Faster runners finishing under 90 minutes may only need one gel or can skip mid-race fuel entirely if their pre-race meal was solid. Slower runners going beyond 2.5 hours should plan for a third fueling window around mile 11.
Foods That Cause Stomach Problems
Gastrointestinal distress is one of the most common reasons runners slow down or drop out. The foods that cause problems tend to fall into a few categories: high fiber, high fat, and common gut irritants. Cruciferous vegetables, whole grains with lots of bran, and greasy or fried foods all take longer to break down and can sit heavily in your stomach during a run.
Caffeine is a gray area. Small amounts can boost performance, and many gels include it intentionally. But if you don’t normally consume caffeine, race day is not the time to start, since it can trigger stomach cramps and urgent bathroom stops. NSAIDs like ibuprofen and naproxen are also worth avoiding before and during a race. Runners sometimes pop them preemptively for soreness, but they’re known to irritate the gut lining and increase the risk of GI problems when combined with the reduced blood flow to your digestive system that happens during hard exercise.
The single most important rule for race-day nutrition: nothing new on race day. Every gel, drink, and pre-race meal should be something you’ve tested on training runs of at least 8 to 10 miles. Your stomach is far less forgiving at race effort than it is during easy running, so rehearsing your fueling plan at goal pace gives you the best shot at a trouble-free race.