Ninety grams of carbohydrate per hour has become the number everyone quotes for long races. It is a real figure from the research, but it comes with conditions. Most athletes cannot just turn up on race day and take it in comfortably.
Here is where the number comes from, who it is meant for, and how athletes usually build up to it in training.
Answer first
- Where 90 g comes from: sports nutrition guidelines suggest up to about 90 g of carbohydrate per hour for events lasting longer than about 2.5 hours.
- The catch: that ceiling assumes a mix of carbohydrate types, usually glucose (or maltodextrin) with fructose. A single type of sugar tends to top out at about 60 g per hour.
- Your gut needs practice: research on "gut training" suggests repeated practice with carbohydrate during exercise can reduce stomach problems.
- It is not for every session: for sessions under an hour, the guidelines suggest much less, and often none is needed.
Where the 90 g figure comes from
A widely cited review by Asker Jeukendrup (2014) set out carbohydrate targets by event duration:
| Session or event length | Suggested carbohydrate |
|---|---|
| Under 45 minutes | Not needed |
| 45 to 75 minutes | Small amounts, or a mouth rinse |
| 1 to 2 hours | Up to 30 g per hour |
| 2 to 3 hours | Up to 60 g per hour |
| Over 2.5 hours | Up to 90 g per hour, from multiple carbohydrate types |
These are upper limits for well-trained athletes, not targets everyone must hit.
Why the mix of carbs matters
Glucose and fructose are absorbed through different transporters in the gut. When a drink relies on glucose or maltodextrin alone, absorption tends to level off at around 60 g per hour. Adding fructose uses a second pathway, which is why products aimed at long events often use a ratio of roughly 2:1 maltodextrin to fructose. More detail is in why dual-carb fuelling works.
Can your stomach handle it?
This is the part that decides race day. A study by Costa and colleagues (2017) found that two weeks of repeated carbohydrate intake during exercise reduced gastrointestinal symptoms compared with a control group. The practical message: if you want to race at 80 or 90 g per hour, practise it on long training sessions first. See our guide to gut training for endurance athletes.
Some researchers are now looking at even higher intakes. A trail marathon study compared 60, 90 and 120 g per hour, but research above 90 g per hour is still limited, so treat it as experimental rather than a new standard.
How athletes usually build up to 90 g per hour
- Start where you are. If you currently take 30 to 40 g per hour, begin there on your long sessions.
- Add about 10 g per hour each week on one or two long sessions, as long as your stomach is happy.
- Practise at race intensity, not only on easy rides. Gut comfort at an easy pace does not always carry over to race pace.
- Use the same products and timing you will race with. Nothing new on race day.
- Spread it out. Small, regular amounts every 15 to 20 minutes usually sit better than a big hit every hour.
What 90 g per hour looks like in practice
- About three to four typical energy gels (most contain 20 to 30 g each).
- One serve of HYDRAX CORE (2 scoops in 600 to 750 ml of water) provides 85 g of carbohydrate in a 2:1 maltodextrin and fructose blend, so one bottle per hour gets you close.
- A mix of drink, gels and solid food, which many long-course athletes prefer.
Work out your own hourly targets for a specific race with the free race fuel plan builder, and see how many carbs per hour for an Ironman for long-course detail.
The short version
Ninety grams per hour is a ceiling for long events, it relies on mixed carbohydrate sources, and it needs to be practised. Build up in training, rehearse at race pace, and race with what you have tested.
Research referenced
- Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine. 2014. https://pubmed.ncbi.nlm.nih.gov/24791914/
- Jeukendrup AE. Training the Gut for Athletes. Sports Medicine. 2017. https://pubmed.ncbi.nlm.nih.gov/28332114/
- Costa RJS, et al. Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism. 2017. https://pubmed.ncbi.nlm.nih.gov/28177715/
- Effects of 120 vs. 60 and 90 g/h Carbohydrate Intake during a Trail Marathon on Neuromuscular Function and High Intensity Run Capacity Recovery. Nutrients. 2020. https://pubmed.ncbi.nlm.nih.gov/32679728/
Important information
This article provides general educational information for healthy adult athletes and is not medical or dietetic advice. Individual carbohydrate tolerance varies. Speak with an Accredited Practising Dietitian for a plan built around you. HYDRAX CORE is a formulated supplementary sports food and should be used with an appropriate training program.
Quick answers
Can you absorb 90 g of carbs per hour?
Guidelines suggest up to about 90 g per hour for events over 2.5 hours when the carbohydrate comes from multiple sources such as glucose or maltodextrin with fructose. Most athletes need to practise in training to tolerate it.
Why do single-sugar drinks top out at 60 g per hour?
Glucose is absorbed through one transporter that tends to level off at around 60 g per hour. Fructose uses a different pathway, so mixing the two allows more total carbohydrate.
How do I build up to 90 g per hour?
Start at your current intake on long sessions and add about 10 g per hour each week, practising at race intensity with the products you will race with.
Do I need 90 g per hour for a short race?
No. For sessions under 45 minutes carbohydrate is not needed, and for 1 to 2 hours guidelines suggest up to 30 g per hour.