Learn how running energy gels work, when to take them and how popular brands compare.
Energy gels are a familiar sight at races, but they are also one of the most misunderstood parts of running nutrition.
Some runners take a gel before every run. Others avoid them completely after one bad experience. Many follow the instructions on the packet without considering how much carbohydrate the product contains or how it fits into their overall fuelling plan.
Used correctly, energy gels provide a convenient source of carbohydrate during longer runs and races. They can help maintain blood glucose, provide fuel to working muscles and delay the drop in performance that can occur when carbohydrate availability becomes limited.
They are not, however, an instant cure for poor pacing, inadequate training, insufficient hydration or starting a race under-fuelled.
The key is understanding when gels are useful, calculating how many you need, choosing an appropriate product and practising your complete strategy before race day.
What is an energy gel?
An energy gel is a small, concentrated serving of carbohydrate designed to be easy to carry and consume while exercising.
Most gels use carbohydrate sources such as:
- Glucose
- Maltodextrin
- Fructose
- Sucrose
- Glucose syrup
- A combination of glucose and fructose
Some products also contain caffeine, sodium or other electrolytes.
A typical gel contains approximately 20–30 grams of carbohydrate, although products vary considerably. One study examining commercially available gels found carbohydrate contents ranging from approximately 18 to 51 grams per serving.
This is why counting gels alone can be misleading. The important number is the amount of carbohydrate in each gel.
Two packets may look almost identical while providing very different amounts. Always check the nutrition label before building a race-fuelling plan.
How do energy gels work?
Carbohydrate is an important fuel for running, particularly when the intensity is moderate to high.
Your body stores carbohydrate as glycogen in the muscles and liver. Muscle glycogen can be used directly by the working muscles, while liver glycogen helps maintain the amount of glucose circulating in the blood.
These stores are limited. As a run becomes longer, carbohydrate availability can begin to fall – especially when you are running at a challenging pace.
The carbohydrate in an energy gel is digested and absorbed into the bloodstream. This provides an additional source of fuel that can be used alongside stored glycogen.
Taking carbohydrate during prolonged exercise can help:
- Maintain blood glucose
- Supply fuel to working muscles
- Support pace and concentration
- Delay fatigue
- Reduce the risk of a severe energy drop
- Make a hard effort feel more manageable
Gels do not instantly refill your glycogen stores, and they will not rescue a race within seconds. This is why it is better to begin fuelling early and consistently instead of waiting until you already feel exhausted.
Do you need energy gels for every run?
No. Most runners do not need energy gels during short or easy runs.
If you have eaten normally beforehand, your body will generally have enough stored carbohydrate to complete a run lasting less than an hour.
A practical starting point is:
| Run duration | Suggested approach |
|---|---|
| Less than 60 minutes | Gels are usually unnecessary |
| 60–90 minutes | Carbohydrate may help during harder efforts but is not always required |
| 1–2.5 hours | Aim for approximately 30–60g of carbohydrate per hour |
| More than 2.5 hours | Experienced runners may benefit from up to 90g per hour after suitable gut training |
These figures refer to your total carbohydrate intake, not just gels. Sports drinks, chews, bars and food must all be included.
Your needs will also be influenced by your pace, training status, pre-run meal, stomach tolerance and environmental conditions.
How many energy gels should you take?
Start by checking how much carbohydrate one gel contains.
You can then use this calculation:
Target carbohydrate per hour ÷ carbohydrate per gel = number of gels per hour
Imagine you want to consume 45 grams of carbohydrate per hour and your gel contains 22 grams:
45 ÷ 22 = approximately two gels per hour
That would mean taking roughly one gel every 30 minutes.
If your target is 60 grams per hour and your gel contains 30 grams, the calculation is even simpler:
60 ÷ 30 = two gels per hour
If the product contains 25 grams, two gels provide 50 grams. The remaining carbohydrate could come from a small amount of sports drink, or you could adjust the timing of your gels.
A four-hour marathon example
A runner targeting 60 grams of carbohydrate per hour over four hours would require:
60g × 4 hours = 240g of carbohydrate
If each gel contains 25 grams, getting all of that carbohydrate from gels would require almost ten gels.
Alternatively, imagine the runner receives approximately 15 grams of carbohydrate per hour from sports drink:
15g × 4 hours = 60g from sports drink
That leaves:
240g − 60g = 180g from gels
At 25 grams per gel, this would require approximately seven to eight gels.
This demonstrates why many marathon runners combine gels with sports drinks or other carbohydrate sources. It can make the strategy easier to follow and reduce flavour fatigue.
You do not need to begin with 60 grams per hour during training. Someone currently taking no carbohydrate might start with 25–30 grams per hour before gradually increasing the amount.
When should you take your first gel?
Do not wait until you feel your energy disappearing.
By the time you feel unusually weak or unable to maintain your expected pace, your carbohydrate availability may already be low. A gel can still help, but the response will not be immediate.
During a longer race, many runners begin consuming carbohydrate within the first 20–30 minutes and continue at regular intervals.
The exact timing will depend on:
- What you ate before the race
- Your hourly carbohydrate target
- The carbohydrate content of the gel
- Whether you are also using sports drinks
- How well you tolerate carbohydrate while running
Setting an alert on your watch can be more reliable than waiting for hunger. Hunger is not always a good indicator of fuelling requirements during hard exercise.
Energy gels by race distance
5K
Most runners do not need a gel during a 5K. The race is too short for consuming carbohydrate partway through to make a meaningful difference.
A suitable pre-race meal or snack is more important.
10K
Most runners will not need a gel during a 10K either. Even when the race lasts slightly longer than an hour, it may be difficult to gain much benefit from a gel taken partway through.
Focus on arriving at the start appropriately fuelled.
Half marathon
Carbohydrate becomes more relevant during a half marathon, particularly for runners who will be racing for longer than 75–90 minutes.
A target of approximately 30–60 grams per hour may be appropriate. Depending on the product, finish time and use of sports drink, this could mean between one and four gels.
Calculate the amount from carbohydrate grams rather than copying another runner’s schedule.
Marathon
Marathon runners should normally have a planned and practised fuelling strategy.
Many recreational runners can gradually work towards approximately 45–60 grams per hour. Experienced runners who have practised higher carbohydrate intakes may use up to 90 grams per hour, normally from a combination of glucose and fructose.
Higher intake is not automatically better. Taking more carbohydrate than your digestive system can tolerate may result in nausea, bloating, cramping or diarrhoea.
Ultramarathon
Gels can be useful during ultramarathons, but relying on them exclusively may become difficult. Sweetness, texture and flavour fatigue can make gels increasingly unappealing after several hours.
Many ultrarunners combine gels with drinks, chews and suitable solid foods. The overall carbohydrate target remains important, but variety can make it easier to maintain.
Why do some gels combine glucose and fructose?
Your intestine uses different routes to absorb different carbohydrates.
Glucose and maltodextrin mainly use one absorption route, while fructose uses another. Combining them can allow the body to absorb and use more carbohydrate than relying on glucose alone.
This becomes particularly useful when attempting higher intakes, such as 60–90 grams per hour during a marathon or ultramarathon.
You may see these products described as containing:
- Dual-source carbohydrates
- Multiple transportable carbohydrates
- A glucose-to-fructose ratio
- A maltodextrin-to-fructose ratio
This does not mean every runner needs a glucose-fructose gel. At lower carbohydrate intakes, a simpler product may work perfectly well.
The best option is one that provides the required carbohydrate and remains comfortable in your stomach.
Should you take energy gels with water?
Most concentrated energy gels should be taken with water unless the manufacturer’s instructions say otherwise.
Water helps dilute the gel and can make it easier to swallow and process. Taking several concentrated gels without fluid may leave some runners feeling sick or excessively thirsty.
Some thinner or isotonic gels are designed to be consumed without additional water. However, they still do not replace your wider hydration needs.
Be careful when taking a concentrated gel with a strong sports drink. This can deliver a large amount of carbohydrate at once and may increase the risk of digestive discomfort.
If you plan to combine gels and sports drinks, practise the exact combination during training.
What about caffeinated energy gels?
Caffeine can improve alertness and endurance performance for some runners, but it is not essential.
Caffeinated gels may be useful later in a long race, when concentration and perceived effort become more challenging. However, individual responses vary considerably.
Possible side effects include:
- Jitters or anxiety
- An increased heart rate
- Nausea
- An urgent need to use the toilet
- Difficulty sleeping after an evening event
Research suggests that relatively modest caffeine doses can support performance, while very high doses are more likely to produce side effects without providing additional benefits.
Check the caffeine content of every gel and include all other sources, such as coffee, sports drinks and pre-workout products.
Avoid taking every gel as a caffeinated gel unless you have calculated and tested your total intake.
People who are pregnant or breastfeeding, sensitive to caffeine, taking certain medications or managing a heart condition should seek appropriate professional advice.
Why do energy gels upset some runners’ stomachs?
Running can place considerable stress on the digestive system.
Blood flow is directed towards the working muscles, movement causes repeated impact, and high exercise intensity can make digestion more difficult.
Common reasons for gel-related stomach problems include:
- Taking too much carbohydrate too quickly
- Swallowing a concentrated gel without water
- Using an unfamiliar product
- Combining gels with more sports drink than planned
- Attempting a high carbohydrate intake without practice
- Running harder than usual
- Starting the race dehydrated
- Consuming an ingredient that does not agree with you
A stomach problem does not necessarily mean you cannot use gels. It may mean the dose, timing, product or accompanying fluid needs to be adjusted.
Can you train your stomach?
Yes. The digestive system can adapt to receiving carbohydrate during exercise.
Research suggests that repeatedly practising a race-fuelling strategy can improve carbohydrate tolerance and reduce gastrointestinal symptoms in some athletes.
Begin during easy long runs rather than an important race:
- Choose one product and check its carbohydrate content.
- Start with a manageable amount, such as one gel per hour.
- Take it with water where appropriate.
- Record how you feel.
- Gradually increase towards your intended race intake.
- Practise at different intensities and in realistic conditions.
- Repeat the same strategy several times before race day.
Record the product, flavour, carbohydrate per hour, fluid intake and any symptoms. This makes it easier to identify what needs changing.
Your fuelling plan should be trained in the same way as your pacing, footwear and equipment.
Are energy gels better than ordinary food?
Energy gels are convenient, but they are not inherently superior to every other carbohydrate source.
Their main advantages are that they are:
- Lightweight
- Easy to carry
- Simple to measure
- Quick to consume
- Low in fibre and fat
- Available in predictable carbohydrate amounts
During faster running, chewing and digesting solid food can be difficult. A gel may therefore be more practical.
During slower ultramarathons or long training days, foods such as bananas, rice-based snacks, sandwiches or other easily digested carbohydrate sources may also work well.
The body is primarily interested in the carbohydrate being provided – not whether it arrived in an expensive packet.
Popular energy gel brands compared
There is no single best energy gel for every runner.
The most suitable option is the one that provides enough carbohydrate, fits into your race plan and does not cause digestive problems.
Carbohydrate content, consistency, caffeine and sodium vary significantly between brands. “Natural”, “isotonic” or “hydrogel” products are not automatically better for everyone.
| Energy gel | Carbohydrate | Caffeine | Main difference |
| SiS GO Isotonic | 22g | None in standard version | Thin isotonic formula |
| SAP25 | 25g | None | Maple syrup and Himalayan salt |
| HIGH5 Energy Gel | 23g | 0mg or 30mg | Wide range of flavours |
| Puresport Energy Gel | 30g | None | 1:0.8 glucose-to-fructose blend |
| Maurten Gel 100 | 25g | None in standard version | Firm hydrogel texture |
| Precision Fuel PF 30 | 30g | None | Mild flavour and simple calculations |
| GU Original Energy Gel | Approximately 23g | 0–40mg depending on flavour | Large flavour range |
SiS GO Isotonic Energy Gel
The SiS GO Isotonic Energy Gel provides 22 grams of carbohydrate in a 60ml sachet. Its carbohydrate comes primarily from maltodextrin.
The product has a thinner, more liquid consistency than many traditional gels. SiS states that it can be consumed without additional water, although runners still require an appropriate hydration strategy.
Pros
- Thin consistency can be easier to swallow
- Can be taken without immediately drinking water
- Available in several flavours
- Standard version is caffeine-free
- Widely available in the UK
- Informed Sport certified
Possible drawbacks
- The 60ml sachet is bulkier than many concentrated gels
- More packets are required to reach higher carbohydrate targets
- The standard version uses one main carbohydrate source
- It contains very little sodium
- The texture and sweetener may not suit every runner
Best suited to: Runners who dislike thick gels or want something that can be taken when water is not immediately available.
SAP GOOD ENERGY
SAP25 is a real-food alternative to a conventional gel. Each sachet provides 25 grams of carbohydrate and 152mg of sodium.
It contains two ingredients: organic Canadian maple syrup and Himalayan salt. Maple syrup naturally provides glucose and fructose in a ratio close to 1:1.
Pros
- Short, recognisable ingredient list
- Provides glucose and fructose
- Contains 25 grams of carbohydrate
- Provides 152mg of sodium
- No caffeine, artificial flavourings or preservatives
- Can also be used before exercise or added to food
Possible drawbacks
- The maple flavour may become repetitive during a long race
- It is not a replacement for water or a complete hydration strategy
- “Natural” does not guarantee easier digestion
- Limited flavour choice may contribute to taste fatigue
- Runners who dislike maple syrup are unlikely to enjoy it
Best suited to: Runners who prefer a simple ingredient list and want carbohydrate with a moderate amount of sodium.
HIGH5 Energy Gel
The HIGH5 Energy Gel provides 23 grams of carbohydrate from glucose syrup and maltodextrin.
Standard flavours are caffeine-free, while HIGH5 Energy Gel Caffeine contains 30mg of caffeine per sachet.
Pros
- Manageable 23-gram carbohydrate serving
- Available with and without caffeine
- Caffeinated versions contain a relatively modest 30mg dose
- Wide variety of fruit flavours
- Suitable for vegetarians and vegans
- Contains no artificial colours or sweeteners
- Compact packet is easy to carry
Possible drawbacks
- Caffeinated and non-caffeinated varieties must be separated carefully
- Several packets are needed to reach 60–90 grams per hour
- It does not provide a substantial amount of sodium
- The glucose-syrup consistency may feel sticky
- Fluid should still be included in the wider plan
Best suited to: Runners looking for an accessible gel with plenty of flavours and a lower-dose caffeine option.
Puresport Energy Gel
The Puresport Energy Gel provides 30 grams of carbohydrate in a 1:0.8 glucose-to-fructose ratio.
Puresport recommends one gel every 30 minutes, which provides 60 grams of carbohydrate per hour.
Pros
- Provides 30 grams of carbohydrate
- Two carbohydrate sources support higher hourly intakes
- One every 30 minutes creates a simple 60g-per-hour plan
- Vegan and gluten-free
- Uses natural flavouring
- Informed Sport certified
- Fewer packets are required than with many gels
Possible drawbacks
- A 30-gram serving may be too much for an unpractised stomach
- The 60g-per-hour strategy should be introduced gradually
- Runners with sensitive stomachs should test the full ingredient list
- Flavour preference remains personal
- A “gut-friendly” formula cannot guarantee no digestive symptoms
Best suited to: Runners targeting around 60 grams per hour who want simple timing and a modern glucose-fructose formula.
Maurten Gel 100
The Maurten Gel 100 contains 25 grams of carbohydrate from glucose and fructose in a 1:0.8 ratio.
Unlike a conventional syrup, Maurten uses hydrogel technology to create a firmer, jelly-like structure. The standard Gel 100 contains six ingredients and has no added flavourings, colours or preservatives.
Pros
- Provides glucose and fructose
- Short ingredient list
- Neutral rather than strongly flavoured
- Four gels provide exactly 100 grams of carbohydrate
- A 40-gram Gel 160 is also available
- Firm texture may be easier to control while running
Possible drawbacks
- The unusual texture can be polarising
- Its neutral taste will not appeal to everyone
- The standard version provides little sodium
- Hydrogel technology does not guarantee no stomach problems
- Gel 100 CAF 100 contains 100mg of caffeine, which must be carefully calculated
Best suited to: Runners who dislike strongly flavoured gels or prefer a firm texture and short ingredient list.
Precision Fuel PF 30 Gel
The Precision Fuel PF 30 Gel provides exactly 30 grams of carbohydrate from maltodextrin and fructose.
It has a mild citrus-based flavour and is designed to reduce stickiness and flavour fatigue. The standard version contains no caffeine or electrolytes.
Pros
- Exactly 30 grams makes planning simple
- Two gels per hour provide 60 grams
- Mild flavour can reduce sweetness fatigue
- Smooth, relatively non-sticky texture
- Uses maltodextrin and fructose
- Vegan, gluten-free and dairy-free
- Informed Sport certified
Possible drawbacks
- The standard gel contains no sodium or caffeine
- Hydration and electrolyte requirements must be managed separately
- A 30-gram serving should be introduced gradually
- The neutral flavour may seem plain
- Larger multi-serving formats require careful measuring
Best suited to: Runners who want simple carbohydrate calculations and separate control over carbohydrate, caffeine and electrolytes.
GU Original Energy Gel
GU Original Energy Gels generally provide around 100 calories and approximately 23 grams of carbohydrate per packet. Exact values should be checked for each flavour.
Depending on the flavour, a gel may contain no caffeine, 20mg or 40mg.
Pros
- Large selection of flavours
- Caffeinated and caffeine-free choices
- Compact packets
- Uses maltodextrin and fructose
- Gluten-free and vegan
- Flavour variety can reduce repetition
Possible drawbacks
- The thick consistency may be easier to consume with water
- Carbohydrate and caffeine content vary by flavour
- Strong flavours may become difficult during longer races
- Caffeinated packets must be identified carefully
- More packets may be needed for higher carbohydrate targets
Best suited to: Runners who want plenty of flavour choices and the option of small or moderate caffeine doses.
Which energy gel should you choose?
Choose according to the practical problem you want the gel to solve:
- For a thinner gel: SiS GO Isotonic
- For a minimal ingredient list: SAP25
- For flavour variety: HIGH5 or GU
- For a simple 60g-per-hour plan: Puresport or Precision Fuel PF 30
- For a neutral flavour and firm texture: Maurten Gel 100
- For some sodium within the gel: SAP25
- For a modest caffeine option: HIGH5 Caffeine or selected GU flavours
- For a larger caffeine dose: Maurten Gel 100 CAF 100, after calculating total intake
These are not performance rankings. A more expensive or technically advanced gel will not automatically improve your running.
Consider buying individual gels or a mixed trial pack before committing to a large box. Test each product during an easy long run before using it at race intensity.
Personal tolerance, carbohydrate content and a repeatable schedule matter more than the brand name.
Common energy-gel mistakes
Waiting until you hit the wall
Gels work best as part of a preventative strategy. Begin fuelling before your energy levels collapse.
Counting gels instead of carbohydrate
Always check the label. Different gels provide different amounts of carbohydrate.
Trying a new product on race day
Ingredients, consistency, sweetness and caffeine content vary. Use the same product in training first.
Taking several gels close together
A sudden large dose may overwhelm your stomach. Spread your carbohydrate across the hour.
Forgetting sports-drink carbohydrates
Sports drinks contribute towards your total. Combining drinks and gels without calculating both can result in taking much more carbohydrate than intended.
Assuming gels replace hydration
Most gels provide very little water. You still need an appropriate drinking strategy.
Copying someone else’s plan
Another runner’s pace, finish time and tolerance may be completely different from yours.
Using only caffeinated gels
Caffeine can accumulate quickly. Check the amount in every product.
A simple way to build your gel strategy
For your next long run:
- Estimate how long you will be running.
- Choose a starting target of approximately 30 grams per hour.
- Check how much carbohydrate is in your gel.
- Include carbohydrate from drinks or food.
- Decide when each serving will be taken.
- Carry suitable water.
- Record your energy levels and stomach comfort.
- Adjust one part of the plan at a time.
Once this feels comfortable, gradually move towards the intake you expect to use during your race.
The bottom line
Energy gels are a practical source of carbohydrate for longer runs and races. They can help maintain carbohydrate availability and support performance, but only when the amount, timing and product are appropriate for the runner.
For most runs lasting less than an hour, gels are unnecessary. For longer events, aim for a planned carbohydrate intake rather than an arbitrary number of packets.
Check the carbohydrate content, start fuelling early, take concentrated gels with water where appropriate and practise everything in training.
The best gel strategy is not the one using the most products or the most expensive brand. It is the one that provides enough carbohydrate, remains comfortable and can be followed consistently when the race becomes difficult.
ENERGY GELS: FREQUENTLY ASKED QUESTIONS
Do I need an energy gel for every run?
No. Gels are usually unnecessary during short or easy runs, particularly if you have eaten normally beforehand. They become more useful during prolonged or demanding sessions when carbohydrate availability may begin to limit performance.
When should I take my first energy gel?
Do not wait until you feel exhausted. Many runners take their first gel within approximately 20–40 minutes of a longer run or race and then continue at planned intervals. Your exact timing should reflect the carbohydrate content of the gel, your target per hour and any sports drink or food you are also consuming.
How many energy gels should I take per hour?
Calculate your intake from carbohydrate rather than simply counting sachets. Most gels contain approximately 20–30g. For exercise lasting one to two-and-a-half hours, a common carbohydrate target is 30–60g per hour, although individual tolerance and requirements vary.
Should energy gels be taken with water?
Most concentrated gels should be taken with water unless they are specifically described as isotonic or the manufacturer states otherwise. Water can make the gel easier to swallow and may reduce digestive discomfort. An isotonic gel still does not replace your overall hydration requirements.
Why do energy gels cause stomach problems?
Possible causes include consuming too much carbohydrate too quickly, insufficient water, unfamiliar ingredients, excessive caffeine or combining gels with more sports drink than expected. Practise during training and increase your intake gradually rather than testing a new strategy on race day.
References and further reading
- Hoffman MD, Stuempfle KJ. Extreme Variation of Nutritional Composition and Osmolality of Commercially Available Carbohydrate Energy Gels. Journal of Athletic Training, 2015. PubMed
- Jeukendrup AE. The Use of Carbohydrates During Exercise as an Ergogenic Aid. Sports Medicine, 2013. PubMed
- Guest NS et al. International Society of Sports Nutrition Position Stand: Caffeine and Exercise Performance. Journal of the International Society of Sports Nutrition, 2021. PubMed
- Miall A et al. Two Weeks of Repetitive Gut-Challenge Reduce Exercise-Associated Gastrointestinal Symptoms and Malabsorption. Applied Physiology, Nutrition, and Metabolism, 2018. PubMed
- King AJ et al. A Systematic Review of Gut-Training Interventions for Improving Gastrointestinal Symptoms and Exercise Performance. International Journal of Sport Nutrition and Exercise Metabolism, 2023. PubMed
- Thomas DT, Erdman KA, Burke LM. Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 2016. PubMed
- Kerksick CM et al. International Society of Sports Nutrition Position Stand: Nutrient Timing. Journal of the International Society of Sports Nutrition, 2017. PubMed
- World Athletics. Consensus Statement: Nutrition for Athletics. 2019. World Athletics
This article is for general educational purposes and does not replace personalised medical or sports-nutrition advice. Runners with diabetes, gastrointestinal conditions, food allergies, caffeine sensitivity or other health concerns should consult an appropriately qualified healthcare professional or sports dietitian. Always check product labels and test your fuelling strategy during training.
Product information checked in August 2026. Ingredients and nutritional values can change, so check the current product label before use.
