Energy Gels for Running: When and How to Use Them

Energy gels provide a compact source of carbohydrate during long runs and races. Most short runs do not need one, but gels can make fuelling easier when you are running hard for more than an hour or spending considerably longer on your feet.

How many you need depends on your running time, the carbohydrate in each packet and anything else you plan to eat or drink. The aim is to build a schedule you have already tested in training. Gels are one part of that plan, alongside what you eat beforehand and how you drink during the run.

Do you need energy gels for running?

Running time is the most useful starting point. Pace, intensity, what you ate beforehand and your tolerance then shape the final decision.

Use these as broad performance guidelines. Someone running easily for 70 minutes after a meal has a different need from someone racing hard for the same time. Comfort and practice matter more than forcing the upper end of a range.

Most runners will not need a gel during a 5K, and a 10K usually needs little or no fuel during the race. Gels become more useful at half marathon and marathon distance as time on feet increases.

What are energy gels and how do they work?

What is in a running gel?

Most energy gels contain concentrated carbohydrate, water, flavouring and a thickening ingredient. The carbohydrate may come from glucose, fructose, maltodextrin or a combination.

A standard packet often provides roughly 20–30 g of carbohydrate, although some high-carbohydrate products contain considerably more. Read the nutrition label because two similarly sized sachets can provide very different amounts.

Some gels also contain caffeine or sodium. A gel with sodium is still mainly a carbohydrate product, while a caffeinated gel needs to be counted alongside other caffeine sources.

What do energy gels do, and how quickly do they work?

Carbohydrate from a gel can be absorbed and used during exercise, helping to keep supplying working muscles with carbohydrate as the run continues. A gel does not instantly refill depleted glycogen stores, and there is no universal moment when it will "kick in". Digestion and absorption vary with the product, effort, heat, fluid intake and the runner.

Some runners notice a lift after taking a gel, while others feel no obvious change. Take carbohydrate according to your plan rather than waiting until you already feel drained.

When should you take energy gels while running?

Build the timing from your carbohydrate plan. Once you know your expected running time, hourly target and carbohydrate per packet, you can spread the servings across the run.

When to take your first gel

For longer runs, start early enough to spread your carbohydrate evenly. If you are aiming for 50 g per hour and each gel contains 25 g, that could mean one gel roughly every 30 minutes, starting around the 30-minute mark. Treat this as an example and adjust it around your drink, breakfast and tested tolerance.

Work backwards from the full schedule rather than saving most of your fuel for the final miles. Test the timing in training and adjust one detail at a time.

Should you take gels by time or distance?

Time is usually more reliable because two runners can take very different times to cover the same distance. An elapsed-time watch alert can help. Distance markers still work when they line up with water stations, but check that the schedule also makes sense in minutes and grams of carbohydrate.

Should you take a gel before running?

A pre-start gel may suit a long race or hard event when breakfast was limited or there has been a long wait since eating. Use it alongside a familiar pre-run meal where possible, count its carbohydrate and caffeine, and test the timing and water in training.

How many energy gels should you take?

Calculate carbohydrate first and packets second. Gel brands vary, and drinks, chews or food may already provide part of what you need.

For example, a two-hour run at 45 g carbohydrate per hour gives a planning total of about 90 g. If the drink you will use supplies 40 g across the run, around 50 g remains. That is equivalent to two gels containing 25 g carbohydrate each.

Record a pre-start gel separately, including its carbohydrate and caffeine. Do not subtract it from the planned during-run amount. The 30–60 g per hour range describes carbohydrate consumed during exercise.

Use the calculation as a starting point. Choose a realistic hourly range for the session, turn the answer into a workable schedule and build towards it in training. Runners new to fuelling may need to start below their eventual race intake.

Count drinks, chews and food too

Drinking carbohydrate at aid stations without counting it can push your intake much higher than planned and increase the chance of stomach trouble. Add every source. If a bottle contains 40 g and you expect to drink half, count roughly 20 g, and check whether the label refers to one scoop or the full bottle.

During-exercise carbohydrate guidance is generally expressed in grams per hour rather than grams per kilogram of body weight. Start with expected duration, your practised hourly intake and the product label.

For the wider carbohydrate picture, read RunFuel's carbs for runners guide.

Should you take energy gels with water?

Follow the instructions for the product in your hand. Standard gels are concentrated and generally designed to be taken with water. Water helps dilute the carbohydrate in the stomach and can make the gel easier to tolerate.

Some liquid or "isotonic" gels are designed for use without additional water, but that does not guarantee they will suit every stomach. You still need a hydration plan.

There is no single correct volume of water per gel. Follow the packet, take sensible mouthfuls when water is available and practise the combination before race day.

Combining a concentrated gel with a strong sports drink can deliver a dense carbohydrate load to the stomach. Water may be more comfortable alongside a standard gel, with sports drink used separately.

Sodium in a gel does not replace water, and electrolytes do not make overdrinking safe. Drink steadily according to thirst, conditions, water access and any known sweat losses. The running hydration guide covers this in more detail.

Gels are sticky and high in carbohydrate. When practical, rinse your mouth with water after taking one. Avoid brushing immediately afterwards; wait at least 30 minutes to allow the tooth enamel to reharden.

How to choose an energy gel

Choose a gel that delivers the carbohydrate your plan expects, fits the available water and feels manageable to open, swallow and carry while running. The loudest performance claim tells you very little about that.

Mixed carbohydrate sources become more relevant at higher intakes, such as 60–90 g per hour. Terms such as hydrogel, "natural" and isotonic do not guarantee faster absorption or fewer stomach problems. Repeated tests in training tell you more than the marketing category.

If you have a food allergy, check the label every time you buy a product. Ingredients and manufacturing warnings can change, so contact the manufacturer if anything is unclear.

If you compete under anti-doping rules, choose independently batch-tested sports products and check the exact batch before use. Batch testing reduces contamination risk but cannot remove it completely.

Caffeinated energy gels

Caffeine can improve endurance performance or reduce perceived effort for some runners, but it is optional and responses vary.

Read the milligrams on the packet. Sports gels and other sports foods can contain roughly 20–100 mg caffeine per serving, and similar-looking flavours may contain different amounts. Add up coffee, tea, energy drinks, pre-workout products and every caffeinated gel planned for the day.

For healthy adults, EFSA reports that single caffeine intakes up to 200 mg and total daily intakes up to 400 mg generally do not raise safety concerns. These are safety reference points, not performance targets, and lower amounts can still cause side effects or disturb sleep.

Test caffeine in training, ideally at the same time of day as the race. It can cause jitters, anxiety, bowel urgency, palpitations or disrupted sleep.

If you are pregnant, the NHS advises having no more than 200 mg of caffeine per day. Speak to a doctor, pharmacist or dietitian if you have a heart condition, experience heart symptoms, take medication that may interact with caffeine or are unsure whether it is appropriate for you. Young runners should get qualified guidance before using caffeinated sports products.

Why energy gels can upset your stomach

A gel is small but concentrated. Stomach trouble can follow when carbohydrate arrives faster than the gut can handle, a concentrated product is taken without enough water or gels are added to an already strong sports drink.

Heat and hard running can make digestion more difficult. Caffeine, unfamiliar sweeteners and product texture may also contribute. Mixed carbohydrate sources can support higher intakes, but a large or unfamiliar fructose intake may trigger symptoms in susceptible runners. Change one variable at a time so the cause is easier to spot.

Use a controlled testing process:

1. Try one product during a familiar long run or steady session where the effort is controlled.
2. Record the carbohydrate and caffeine per packet, when you took it and what you drank.
3. Note energy, nausea, bloating, cramps, reflux and bowel urgency during and after the run.
4. Change one variable at a time, such as timing, water, product or total carbohydrate.
5. Gradually practise the intake and conditions you expect on race day.

Practising carbohydrate intake repeatedly in training may improve tolerance and reduce stomach discomfort for some runners. The evidence is promising but not consistent, so increase your intake gradually and track your own response.

Frequent, severe or unpredictable gut symptoms deserve personalised support. Speak to a GP, HCPC-registered dietitian or SENR-registered sport and exercise nutritionist if symptoms persist, and seek prompt medical advice for blood in the stool, repeated vomiting, fainting or severe abdominal pain.

Alternatives to energy gels

Gels are only one portable carbohydrate option. Sports drinks, chews, sweets, bananas and dates may also work when practised. Food can be harder to chew, carry or tolerate at higher intensities, so choose around the run, water access and your stomach.

You can also combine formats. A drink may provide part of the hourly carbohydrate target, with a gel or chew covering the remainder. Keep counting the total rather than treating each product as a separate plan.

For a fuller comparison, read RunFuel's running fuel guide.

Building your race-day gel plan

Your plan should be easy to follow when you are tired and still work if you miss a water station or run more slowly than expected. Build it around a realistic finish-time range.

Before race day, check:

• Your realistic expected running time.
• The carbohydrate range you have practised per hour.
• Carbohydrate and caffeine in every gel, drink, chew or food serving.
• The timing of each serving, written in elapsed time.
• Aid-station locations and what each station supplies.
• Which gels need water and where that water will come from.
• How you will carry and open the packets, and where wrappers will go.
• Your total caffeine from breakfast through to the finish.
• Whether one spare serving is practical in case a packet is dropped or damaged.

Run the plan in training more than once using the same breakfast, products, timing and water setup. Where practical, test it at a similar intensity and in conditions close to those expected on race day.

When to get personalised advice

Speak to an HCPC-registered dietitian, SENR-registered sport and exercise nutritionist, GP or relevant healthcare professional if you have diabetes, a gastrointestinal condition, severe allergies, a history of disordered eating or a medical condition that affects food, fluid or caffeine choices.

Professional advice is also appropriate if gels repeatedly cause vomiting, diarrhoea, severe pain, dizziness or fainting, or if anxiety around race fuelling is making it difficult to eat enough. Energy gels are sports foods, not a treatment plan for a medical condition.