The low point in an ultramarathon rarely arrives because you suddenly forgot how to run. More often, it starts hours earlier: a missed bottle, a gel you could not stomach, too little sodium in the heat, or a pace that demanded more carbohydrate than you replaced. Knowing how to fuel ultramarathons means building a plan that protects your energy, hydration, and decision-making long before the race feels hard.
Ultra fueling is not about finding one miracle product. It is about matching intake to duration, terrain, temperature, intensity, sweat loss, and the foods your gut can handle at race effort. Train it with the same discipline you bring to climbing, pacing, and downhill durability.
Start With Carbohydrates Per Hour
Carbohydrate is the main race-day fuel for sustained work above easy conversational effort. Your body stores a limited amount as glycogen in muscle and liver. Once those stores fall too far, pace drops, perceived effort rises, and even simple decisions can become difficult.
For many ultrarunners, a practical starting target is 60 to 90 grams of carbohydrate per hour. Athletes racing aggressively, especially in events with runnable terrain, may tolerate and benefit from 90 grams or more per hour when they have trained their gut for it. On slower, highly technical courses, or during periods of stomach distress, the workable number may be lower. The goal is not to force an impressive target. It is to sustain the highest intake you can absorb comfortably.
Start early. Take in carbohydrate within the first 20 to 30 minutes, then keep it coming in small, repeatable doses. Waiting until you feel depleted is a losing strategy because digestion and absorption cannot instantly erase an energy deficit.
Gels, drink mixes, chews, bars, bananas, rice-based foods, potatoes, broth, and aid-station options can all fit. A gel-and-drink-mix approach makes intake easier to measure. Real food can provide variety and help athletes who develop flavor fatigue after several hours. Most successful plans use both, with familiar products serving as the foundation.
Use Multiple Carbohydrate Sources When Needed
At higher hourly carbohydrate intakes, products that combine glucose or maltodextrin with fructose can improve total absorption compared with relying on one carbohydrate pathway alone. This matters most when you are targeting the upper end of fueling, not when you are jogging through a 50K at low intensity.
Read labels and do the math before race day. A flask of drink mix, two gels, and a handful of chews may sound like plenty, but it could be either 40 grams or 100 grams of carbohydrate depending on the products. Build your plan in grams per hour, not vague intentions.
Hydration Is Individual, Not a Contest
Drinking more is not automatically better. Both dehydration and overdrinking can damage performance, and excessive plain-water intake can dangerously dilute blood sodium. Your hydration plan should reflect your sweat rate, weather, access to aid stations, and personal comfort.
A useful training exercise is to weigh yourself before and after a one-hour run in conditions similar to your target event. Account for the fluid you drank during that hour. The difference offers an estimate of sweat loss, not a command to replace every ounce in real time. In many circumstances, drinking to thirst while maintaining a planned bottle schedule works well, especially when paired with regular assessment of heat, urine output, thirst, and body sensation.
On cooler mountain courses, you may need less fluid but still require consistent calories. In hot, humid races, fluid demands can rise sharply while stomach capacity does not. That is where concentrated fuel plus a deliberate water plan, or a lighter carbohydrate drink mix, can make execution simpler.
Do not test a new hydration system during race week. Bottle carry, vest pockets, soft flasks, powder packets, and refill timing should all be second nature by the start line.
Match Sodium to Your Sweat Loss and Conditions
Sodium supports fluid balance, nerve signaling, and muscle function. It is especially relevant during long races in heat, for runners with salty sweat, and for athletes who lose substantial fluid over many hours. But sodium is not a substitute for carbohydrate, and taking more capsules will not fix underfueling.
A broad starting range is 300 to 800 milligrams of sodium per hour, with some heavy and salty sweaters requiring more in hot conditions. The right amount depends on your individual sweat sodium concentration, rate of fluid loss, diet, race duration, and what is already included in your drink mix and food.
Look for practical clues during training: salt crust on clothing, frequent cramping in hot races, headaches associated with excessive plain water, and large fluid losses may justify a more intentional sodium strategy. Cramping, however, is complex. It can also reflect fatigue, pacing, muscular damage, or insufficient conditioning. Do not assume every cramp is an electrolyte emergency.
Add every source together. If your drink mix supplies sodium, your gels contain some, and you also use electrolyte capsules, calculate the total. Precision beats random capsule timing.
Practice Your Race Fuel Under Stress
Your gut is trainable. A fueling plan that feels fine on an easy two-hour run can fail during a hard long run, in summer heat, or after six hours of movement. Include race-style fueling in key workouts, particularly long runs, back-to-back long days, race-pace climbing sessions, and heat-acclimation blocks.
Practice the exact flavors, textures, and concentrations you plan to use. Train with the aid-station foods if they are available in advance. If you know you cannot tolerate a popular drink or gel, there is no performance advantage in forcing it because other athletes use it.
Keep a simple post-workout record: carbohydrate per hour, fluid volume, sodium intake, caffeine, weather, intensity, GI symptoms, energy level, and what you would change. After a few long sessions, patterns become obvious. You may find that liquid calories work early but solid food sits better late, or that a sweeter flavor becomes intolerable after hour five.
Build a Plan for the Hours Before the Start
The work begins before the gun. In the 24 to 48 hours before an ultra, prioritize carbohydrate-rich meals you know digest well. You do not need an extreme eating contest. You need full glycogen stores without creating unnecessary GI distress from unfamiliar foods, excessive fiber, or oversized portions.
Eat a familiar pre-race meal about two to four hours before the start. Most athletes do well with carbohydrate-forward foods that are relatively low in fat and fiber, plus a normal amount of fluid. If your race starts before dawn, use the timing you have practiced. A smaller meal closer to the start can work if that is your routine.
Carry enough fuel to cover the first segment even if aid stations are delayed, crowded, or unexpectedly short on your preferred options. In an ultra, self-sufficiency is a performance advantage.
Use Caffeine With a Purpose
Caffeine can improve alertness, perceived effort, and late-race focus. It can also cause anxiety, nausea, urgency, disrupted pacing, and a rough crash when used without a plan. Treat it as a tool, not as a substitute for sleep or calories.
Many athletes save caffeine for the second half, overnight sections, or a decisive late-race climb. Doses vary widely, but smaller repeated amounts are often easier to tolerate than one large hit. Count caffeine from gels, chews, drink mixes, coffee, and tablets together. Practice your approach in training, especially if you are prone to GI issues or have medical reasons to limit stimulant use.
For tested athletes, choose products carefully and review their ingredient and quality-assurance practices. A label claim alone is not a guarantee of competition compliance. ProLine Sports Nutrition emphasizes performance products from established endurance brands, but every athlete remains responsible for checking what they use under their governing body’s rules.
Adjust When the Plan Meets Reality
A race plan is a starting point, not a script you follow blindly. If nausea develops, slow your intake briefly rather than abandoning calories for hours. Reduce concentration by taking water, switch textures or flavors, walk a climb to lower intensity, and restart with small doses. If you are overheating, prioritize cooling, fluid, and a manageable carbohydrate source.
If you are suddenly ravenous, shaky, irritable, or unable to hold pace, increase carbohydrate before blaming your fitness. If your stomach is sloshing, examine whether you are drinking too much too quickly, using an overly concentrated mix, or pushing harder than your gut can support.
The strongest ultrarunners are not the ones who endure the most discomfort without adapting. They are the ones who recognize a problem early and make a calm, measurable correction.
Your next long run is the right place to rehearse. Choose your hourly carbohydrate target, calculate what is in each bottle and packet, set a timer if needed, and learn what your body can execute when the miles get serious. Race day should not be the first time you ask your gut to perform like an ultrarunner.