How Many Carbs per Hour Do You Need in Endurance Events?

Short answer: it depends on how long you'll be going. For about an hour, you need little or nothing. For one to two hours, up to about 30 g of carbohydrate an hour, or up to 60 g in some guidelines; for two to three hours, up to about 60 g. Beyond about two and a half hours, aim for up to 90 g an hour, from a mix of glucose and fructose, which some sports drinks and gels contain (check the label) (1, 2). For a half-Ironman, that might mean one bottle of sports drink and one gel an hour on the bike (about 65 g) while you're building up, and a second gel an hour (about 90 g) once your gut is used to it. Trained athletes who have practised fuelling may manage up to 120 g, but that is newer evidence and not yet the standard advice (3).

In long events, carbohydrate taken during exercise helps you hold the pace for longer before fatigue sets in (3). Stomach problems are also common in endurance events, and the gut needs practice to handle larger amounts (4). The targets are in grams per hour, not per kilogram of body weight. The main limit is how fast your gut and liver can pass carbohydrate into the blood, not how big you are (1, 5). Fitness alone doesn't raise that limit, but practice may (4). The evidence is early (6), but practising is common coaching practice.

What most amateurs should do: as a coaching starting point, take about 30 g an hour in sessions over about 75 minutes. For an event over 2.5 hours, aim to be comfortable at 60 g an hour before race day, and build towards 90 g only if your stomach allows. A plan you can stomach beats a bigger number you can't.

How much should you take per hour?

Under about half an hour, you don't need any. Beyond that, these targets mostly follow Jeukendrup's guidelines (the last row is newer), by how long your event lasts:

Event duration	Carbohydrate per hour	What kind
30 to 75 minutes	Small amounts, or a mouth rinse	Any
1 to 2 hours	Up to 30 g (others: 30–60 g)	A single source such as glucose is fine
2 to 3 hours	Up to 60 g	A single source is fine
Over 2.5 hours	Up to 90 g	Glucose plus fructose
Over 2.5 hours, trained and practised	Up to 120 g (emerging)	Glucose plus fructose

Glucose and fructose are two simple sugars that your gut absorbs by different routes, which is why the mix matters at high amounts (explained below). Maltodextrin, which you'll see on many labels, is a chain of glucose and counts as glucose here.

The first four rows follow the guidelines of sports-nutrition researcher Asker Jeukendrup (1). An earlier review by Burke and colleagues broadly agrees: 30 to 60 g an hour for longer events, and up to 90 g beyond 2.5 hours (2). A 2016 joint statement from three major sports-medicine and dietetics bodies gives the same 90 g ceiling (7), as summarised in a 2026 review (3). The 120 g row is that 2026 review's suggestion for trained athletes (3).

Between 2.5 and 3 hours the rows overlap. As a rule of thumb, go nearer 60 g if you're new to fuelling or going easy. Go nearer 90 g, from a glucose-fructose mix, if you've practised and are racing hard.

If you're experienced: work up towards the top of your row over several weeks of long sessions, and only try more than 90 g an hour if you've trained your gut and the event is long enough to need it.

At low intensities, such as an easy long ride, you burn less carbohydrate per hour, so the targets may need adjusting down (1). In our coaching view, if you'll be out for many hours at a moderate pace, 60 to 90 g is a more realistic ceiling than 120 g, which comes from trained athletes (3).

Ultras are where the guidance differs most. Jeukendrup's guidelines go up to about 90 g an hour (1). The International Society of Sports Nutrition's ultra-marathon position stand suggests 30 to 50 g an hour, with a little protein and a variety of foods (8). Let your pace and your gut decide where you sit.

Why the amount depends on duration

In about an hour of hard exercise, your stores of carbohydrate in the muscles and liver (glycogen) don't run out. A systematic review of 61 performance studies concluded that the benefit there seems to come largely through the brain: carbohydrate in the mouth may signal reward centres, so even rinsing a sports drink round your mouth and spitting it out can help a little (9). In events this short, the type and amount you swallow seem to matter less.

In longer events, the liver's glycogen and then blood sugar can run low, and carbohydrate taken during exercise helps by sparing liver glycogen and keeping blood glucose up, so your muscles can keep using carbohydrate late in the event (3). The 61-study review also found that the performance benefit of carbohydrate grew with the length of exercise (9).

The bottleneck is absorption. Glucose gets from your gut into your blood through one type of carrier, a bit like a single-lane road (the liver may also set a limit). It is full at around 60 g an hour, so eating more glucose doesn't raise how much you burn (1, 5). Fructose uses a different route, so combining the two lets more get through. In lab studies, all in men and mostly in cycling, drinks mixing fructose with glucose at high intakes (about 80 g an hour or more) gave small to moderate gains in power output and fewer stomach problems than the same amount of glucose alone (10). Whether mixes help at lower intakes, or in women, hasn't been well tested.

Building your race fuelling plan

Work it out from your expected finishing time, then turn grams into products.

1. Pick your hourly target from the table. A 4-hour marathon or a half-Ironman: 60 to 90 g an hour. A 2-hour half marathon: up to about 30 g, though up to 60 g is within other guidelines (2, 11).
2. Read the labels. Gels, bars and drink mixes list carbohydrate per serving, and many sports products list glucose (or maltodextrin) and fructose. Ratios of about 1:0.5 to 1:1 glucose to fructose were the ones studied (10). If the ingredients list only glucose, dextrose or maltodextrin, it's a single source; sucrose (table sugar), honey and fruit also contain fructose. Above about 60 g an hour, make sure your products include fructose; otherwise stay nearer 60 g (1).
3. Do the arithmetic. Say your gel has 25 g and your bottle of sports drink 40 g. One bottle plus one gel an hour is 65 g; add a second gel and you're at 90 g.
4. Spread it out. As a rule of thumb, small amounts every 15 to 20 minutes sit better than a large amount once an hour, and gels go down better with a few mouthfuls of water. For drinks in long, hard sessions, one position stand suggests about 180 to 350 mL every 10 to 15 minutes (11), but the upper end is a lot of fluid. Base how much you drink on your own sweat rate and thirst, and don't drink more than you lose: overdrinking in long events can dangerously lower blood sodium (8).
5. Match it to the course. Set a timer, plan where you'll take what, and know which products the event offers at aid stations.

Drinks, gels or food? Carbohydrate can come from liquids, gels or solid food; all can work (1).

In a triathlon, a common coaching approach, not a tested protocol: start eating 15 to 20 minutes into the bike, once your breathing has settled after the swim. Aim for the top of your hourly target on the bike, where eating is easier, and keep taking about 30 to 60 g an hour on the run, mostly from gels and sports drink. Don't try to make up on the run what you missed on the bike.

For example, in a half-Ironman with a 3-hour bike and a 2-hour run, using the products above: on the bike, one bottle and one gel an hour (65 g) if you're still building up, or one bottle and two gels (90 g) if you've trained your gut to it, so three bottles and three to six gels in all. On the run, a gel every 30 minutes (50 g an hour) with water or sports drink at aid stations. Carry what the course doesn't provide.

In training, use the table as a guide for long or hard sessions; easy rides may need less. In the weeks before a long race, your long sessions are where you practise your race amount.

How to train your gut

Your gut adapts, though most of the evidence is early. Practising carbohydrate intake during exercise seems to make the stomach more comfortable, and animal studies suggest a high-carbohydrate diet increases the gut's glucose carriers (4). Direct evidence in people that absorption improves is still limited.

A systematic review found only eight studies of gut training. In the two that used a two-week programme of repeated carbohydrate feeding during exercise, gut discomfort fell by about half; effects on gut symptoms were unclear in most of the others (6). The evidence is promising but thin.

If you have diabetes or a diagnosed gut condition, or you know fructose upsets you, plan this with your doctor or a registered sports dietitian before you start.

A practical progression, which is coaching practice rather than a tested protocol:

• Start 10 to 12 weeks before the race: take your current comfortable amount in every session longer than about 75 minutes.
• Each following week: add about 10 g an hour in your long sessions (at least one long ride or run a week), as long as your stomach stays settled, until you reach your race target. Starting at 30 g, that's 40 g in week 2, 50 g in week 3, and 90 g by week 7, in time for the rehearsals.
• In the last 4 to 6 weeks, but not in the taper: rehearse the race plan, with the same products and timings, in two or three long sessions. Do one of them at race pace, lasting half to two-thirds of your expected race time, rather than as a full-distance simulation. Do it at least 10 to 14 days before the race.

If you get cramps, nausea or diarrhoea, drop back to the last amount that worked and build more slowly. Persistent or severe gut symptoms are worth discussing with a doctor or a registered sports dietitian.

What if…

…your race is shorter than an hour? You don't need to eat during it. A mouth rinse or a few sips of sports drink may help a little (9); eat normally beforehand.

…you get stomach problems in every race? Check a few things before blaming the product: whether you took more than you've practised, whether you took it in big gulps rather than little and often, whether you'd practised at race intensity, whether you took gels without water, whether you were dehydrated or racing in heat, what you ate beforehand, and whether you took anti-inflammatory painkillers (8). Then try a product with a glucose-fructose mix (10). Some people tolerate fructose poorly; if a mix makes things worse, see a registered sports dietitian, who can also judge whether a supervised diet low in certain fermentable carbohydrates (a low-FODMAP diet) is worth trying (8).

…you want to try more than 90 g an hour? It hasn't yet been shown to make you faster in races (3, 12), so most amateurs don't need to. In a randomised trial, 20 elite male mountain runners who had done gut training took 60, 90 or 120 g an hour during a mountain marathon, with six or seven in each group. Those on 120 g had lower blood markers of muscle damage the next day, and reported a lower perceived exercise load (how hard the race felt, multiplied by its duration). Finishing times did not differ significantly between the groups (12). A 2026 review concluded that 120 g an hour may be a reasonable upper limit for trained athletes, but that the 120 to 200 g some athletes now try is not supported by research (3).

…you're training rather than racing? Not every session needs race-level fuelling. How you fuel training is a separate question, covered in our article on periodising nutrition.

The science behind it

Optional reading, for anyone who wants the detail.

Tracer studies, which label the carbohydrate athletes drink so researchers can see how much is burned, show that glucose, sucrose, maltose and maltodextrins are oxidised (burned for energy) at high rates, and fructose and galactose at 25 to 50% lower rates. Increasing intake of a single sugar beyond about 1 to 1.5 g a minute (60 to 90 g an hour) doesn't raise oxidation above about 1 to 1.1 g a minute, which points to a limit in the gut or liver rather than the muscle (5).

Rowlands and colleagues' critical review of 14 studies of 2.5 to 3 hours of exercise found the largest performance gains from fructose-glucose mixes at higher intakes: at 1.7 g a minute or more (about 100 g an hour), drinks with about half as much fructose as glucose improved mean power in lab performance tests by about 4 to 9% compared with glucose alone, against 1 to 3% at 1.4 to 1.6 g a minute; lab gains don't translate directly into race time. All 14 studies were in men, and confidence intervals were wide (10).

On gut training, one study of 16 trained cyclists and triathletes found that those who took carbohydrate during their daily training for 28 days burned more of the glucose they drank during exercise afterwards. A group matched for total energy, who ate less carbohydrate across the whole day and none during training, did not. Performance improved by a similar amount in both groups, so the change showed up in fuel use, not results (13).

The case for 120 g an hour rests mainly on higher oxidation rates at those intakes, with possible effects on durability and economy, rather than on many race-performance trials (3). The 2017 position stand on nutrient timing recommended 30 to 60 g an hour for long, hard exercise (11), while earlier reviews had already set the ceiling at 90 g for events over 2.5 hours (1, 2). The core principle hasn't changed: match the dose to how long you're going, and practise it.

References

1. Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med. 2014. doi:10.1007/s40279-014-0148-z
2. Burke LM, Hawley JA, Wong SH, et al. Carbohydrates for training and competition. J Sports Sci. 2011. doi:10.1080/02640414.2011.585473
3. Morton JP, Fell JM, Gonzalez JT, et al. From Metabolism to Medals: Contemporary Perspectives and Revisiting Carbohydrate Guidelines for Fueling Endurance Athletes during Exercise. J Nutr. 2026. doi:10.1016/j.tjnut.2026.101442
4. Jeukendrup AE. Training the Gut for Athletes. Sports Med. 2017. doi:10.1007/s40279-017-0690-6
5. Jeukendrup AE, Jentjens R. Oxidation of carbohydrate feedings during prolonged exercise: current thoughts, guidelines and directions for future research. Sports Med. 2000. doi:10.2165/00007256-200029060-00004
6. Martinez IG, Mika AS, Biesiekierski JR, et al. The Effect of Gut-Training and Feeding-Challenge on Markers of Gastrointestinal Status in Response to Endurance Exercise: A Systematic Literature Review. Sports Med. 2023. doi:10.1007/s40279-023-01841-0
7. Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016. doi:10.1249/mss.0000000000000852
8. Tiller NB, Roberts JD, Beasley L, et al. International Society of Sports Nutrition Position Stand: nutritional considerations for single-stage ultra-marathon training and racing. J Int Soc Sports Nutr. 2019. doi:10.1186/s12970-019-0312-9
9. Stellingwerff T, Cox GR. Systematic review: Carbohydrate supplementation on exercise performance or capacity of varying durations. Appl Physiol Nutr Metab. 2014. doi:10.1139/apnm-2014-0027
10. Rowlands DS, Houltham S, Musa-Veloso K, et al. Fructose-Glucose Composite Carbohydrates and Endurance Performance: Critical Review and Future Perspectives. Sports Med. 2015. doi:10.1007/s40279-015-0381-0
11. Kerksick CM, Arent S, Schoenfeld BJ, et al. International society of sports nutrition position stand: nutrient timing. J Int Soc Sports Nutr. 2017. doi:10.1186/s12970-017-0189-4
12. Viribay A, Arribalzaga S, Mielgo-Ayuso J, et al. Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon on Exercise-Induced Muscle Damage in Elite Runners. Nutrients. 2020. doi:10.3390/nu12051367
13. Cox GR, Clark SA, Cox AJ, et al. Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. J Appl Physiol (1985). 2010. doi:10.1152/japplphysiol.00950.2009