Nausea around mile 18 can ruin an otherwise well-planned marathon, especially when you are already using Maurten gels on a regular schedule. The problem is not always the brand or the gel itself. Gel concentration, how much fluid you drink, running intensity, heat, and the total amount of carbohydrate reaching your stomach can all combine at the same point in a race.
This guide gives you a practical plan for troubleshooting Maurten gels before marathon day. The aim is not to force more fuel down. It is to find the lowest-risk combination of gel type, timing, water, pace, and conditions that your stomach can handle.
Quick Answer
If Maurten gels make you nauseous around mile 18, first test whether the issue is concentration, timing, or intensity rather than immediately abandoning the product. Take each gel with the amount of water recommended for that product, avoid stacking gels too closely, and practice the exact plan during long runs.
A common starting adjustment is to use smaller, more evenly spaced carbohydrate doses instead of waiting until you feel depleted and then taking several gels close together. Slow slightly before fueling, take the gel with water when appropriate, and avoid washing it down with a large volume all at once.
Also test your marathon pace in similar conditions. Nausea that appears at the same distance may be caused by rising effort, heat, dehydration, or reduced stomach blood flow rather than one particular gel. Change one variable at a time so you can identify the real trigger.
Why This Happens
The gel may be too concentrated for your stomach
Maurten products are designed around a hydrogel system, but they still contain carbohydrate that must be digested and absorbed. A gel taken without enough fluid can leave a concentrated mixture in the stomach. For some runners, that contributes to heaviness, reflux, cramping, or nausea.
The exact fluid requirement depends on the product. Maurten Gel 100 and Gel 100 CAF 100 are commonly used without the same large water requirement associated with more concentrated drink mixes, while Gel 160 contains more carbohydrate per serving. Read the package instructions and test the product as directed rather than assuming every gel should be taken in the same way.
Too much carbohydrate arrives too quickly
A regular schedule can still be too aggressive if each dose is large or if the timing creates a sudden carbohydrate load. For example, taking a gel every 30 minutes may work for one runner but feel excessive for another, particularly if the runner is also drinking a sports drink.
Nausea often appears late because the total load has built up. Earlier gels may seem fine, but the stomach can become less tolerant as the run continues and fatigue increases.
Marathon effort slows digestion
During hard running, blood flow is directed toward working muscles and skin, especially in warm weather. Digestion may become less efficient. A gel that feels comfortable at an easy long-run pace can feel unpleasant at marathon effort.
If you take a gel while breathing hard or climbing a hill, you may swallow more air and give your stomach less time to process it. The result can be bloating or nausea even when the fueling plan looked sensible on paper.
Heat and dehydration change the equation
Heat increases sweating and cardiovascular strain. Dehydration can make gastrointestinal symptoms more likely, but drinking too much plain water at once can also cause discomfort. The goal is not to chase a fixed number of ounces regardless of conditions. It is to practice a measured drinking pattern that matches your sweat rate, weather, and race aid stations.
The pace may be slightly too fast
Mile 18 is a common point for problems because a small pacing error from the start has accumulated. If your effort is above sustainable marathon intensity, nausea may be an early warning sign of overall overload rather than a simple fueling failure.
A useful test is to compare runs where you use the same gel plan at different paces. If the nausea disappears when you run 10 to 20 seconds per mile slower, intensity deserves attention before you add more fuel.
Step-by-Step Method
1. Record the full fueling picture
For your next long run, write down:
- Gel type and carbohydrate amount
- Time or distance of every gel
- Sports drink, water, and caffeine intake
- Pace and major hills
- Temperature, humidity, and sun exposure
- When nausea, bloating, reflux, or cramping begins
Do not record only the gel brand. A gel may be blamed because it is the most visible part of a larger plan involving breakfast, coffee, drink mix, and race intensity.
2. Calculate your approximate carbohydrate intake
Add the carbohydrate from gels, sports drinks, chews, and other fuel. Many marathon runners aim somewhere in the broad range of 30 to 60 grams of carbohydrate per hour, while experienced athletes may tolerate more with specific training. More is not automatically better.
Use the lower end of a sensible range if your stomach is sensitive, then increase gradually only if your training supports it. The target should fit your experience and tolerance, not just a plan copied from another runner.
3. Check the product instructions
Confirm whether you are using Gel 100, Gel 100 CAF 100, Gel 160, or another product. Note the carbohydrate amount and caffeine content. A caffeinated gel may be useful late in a marathon, but caffeine can aggravate nausea, reflux, shakiness, or urgency for some runners.
Do not introduce a new caffeine dose on race morning. If you use a caffeinated gel, test it during a long run at a similar time and effort.
4. Move the first fuel earlier if necessary
Waiting until mile 8, 10, or until you feel tired can lead to larger doses later. A small, planned intake early in the run is often easier than trying to catch up after energy levels drop.
A practical pattern might be a gel after the first 30 to 40 minutes, followed by smaller doses at consistent intervals. The right schedule depends on the carbohydrate per gel and your hourly target. Avoid changing both the gel amount and timing dramatically in the same test.
5. Pair fuel with a controlled drinking plan
Take water in small, repeatable amounts at aid stations instead of alternating between long periods without fluid and a large gulp. If the product instructions call for water, take the gel near an aid station so you can drink shortly afterward.
Do not force excessive water to compensate for a concentrated gel. Too much fluid sloshing in the stomach can be just as uncomfortable. Practice with the cup size and drinking speed likely to be available during your race.
6. Slow down briefly when taking the gel
Reduce your effort for 30 to 60 seconds, relax your breathing, and take the gel in manageable swallows if needed. A short pace adjustment is not a failure. It may help you fuel without turning the moment into a high-intensity swallowing exercise.
Avoid taking a gel immediately before a hill or during a hard surge. Choose a flatter section when possible.
7. Test one change at a time
Use at least three long-run tests when your schedule allows:
- Keep the product and timing, but add the correct amount of water.
- Keep the product and water, but reduce the dose or space it farther apart.
- Keep the successful fueling plan and test it at marathon effort in warmer conditions.
Changing everything at once makes the result hard to interpret. You want to know whether the problem was concentration, dose, caffeine, timing, pace, or weather.
8. Build a race-week safety plan
The final week is not the time to experiment with a new gel, a new breakfast, or a much higher carbohydrate target. Use the product and flavors you have already tolerated. Pack enough familiar fuel, but do not carry so much that you feel pressured to consume every packet.
Check the race course map. Decide which aid stations have water, where your fuel will be stored, and whether you will carry your own bottle. A simple plan reduces rushed decisions when fatigue starts.
Common Mistakes
Taking a gel only after feeling weak
By the time you feel empty, you may be tempted to take a gel quickly and chase it with a large drink. This can overload your stomach. Take smaller, planned doses before the crash instead.
Treating every gel as interchangeable
Gel 100, Gel 160, caffeinated gels, sports drinks, and chews do not provide the same carbohydrate or caffeine load. Read the label and calculate the complete hourly intake instead of counting packets.
Drinking too much water at once
A large amount of water can create sloshing, bloating, and nausea. Use small, practiced amounts at regular opportunities. Adjust for weather and sweat rate rather than following a rigid formula.
Ignoring pace because the fueling plan looks perfect
A nutrition plan cannot fully compensate for starting too fast. If nausea begins alongside unusually high breathing effort, easing the pace may help more than adding another gel.
Trying to fix the problem during race week
Last-minute product changes create uncertainty. Make your final meaningful test at least several days before the race, and keep race-week choices familiar.
Checklist or Decision Table
| Symptom or pattern | Likely variable to test | Practical adjustment | What to monitor |
|---|---|---|---|
| Nausea soon after a gel taken without water | Concentration | Follow the product directions and take it near a water station | Whether symptoms improve within the next hour |
| Nausea after several successful gels | Total carbohydrate load | Reduce dose size or increase spacing; count sports drink too | Grams per hour and stomach comfort |
| Symptoms are worse with caffeinated gels | Caffeine tolerance | Use non-caffeinated fuel or test a smaller caffeine dose | Nausea, jitters, reflux, and heart rate sensation |
| Nausea appears during hills or surges | Effort and swallowing | Fuel on flatter ground and ease effort briefly | Breathing and pace at the time of intake |
| Symptoms are worse in heat | Fluid and heat strain | Practice drinking regularly and start more conservatively | Weather, thirst, sweat, and pace |
| Symptoms appear at the same mile every time | Cumulative load or pacing | Review early pace, total intake, and timing before mile 18 | First symptom, not just the point of failure |
When This Advice Does Not Apply
This troubleshooting plan is for common exercise-related fueling discomfort, not a diagnosis. Stop running and seek appropriate medical help for severe or persistent symptoms, repeated vomiting, fainting, confusion, chest pain, severe abdominal pain, bloody stool, or signs of serious heat illness.
Do not continue experimenting if nausea comes with an injury, illness, or symptoms that are unusual for you. A sports dietitian can help build a personalized carbohydrate and hydration plan, especially if you have a gastrointestinal condition, diabetes, kidney concerns, or medication-related restrictions.
The advice also may not apply if the real problem is your pre-run meal. A large, high-fat, high-fiber, or unfamiliar breakfast can remain in the stomach during a marathon. Test breakfast timing and ingredients separately from your gel plan.
Finally, do not assume that more fuel is necessary simply because a calculator recommends it. Your ability to absorb carbohydrate must be trained. A lower intake that you can tolerate may be more useful than an ambitious target that causes nausea.
Realistic Example
Consider a runner preparing for a marathon who uses one Maurten Gel 100 every 30 minutes. The runner also drinks sports drink at several aid stations and takes a caffeinated gel late in the race. The first symptoms appear around mile 18, usually after a warm-weather section and a small pace increase.
Instead of replacing all the gels, the runner reviews the total carbohydrate intake and discovers that the sports drink adds more than expected. In the next long run, the runner keeps the same gel but spaces doses slightly farther apart, uses water rather than sports drink at selected stations, takes the gel on a flatter section, and holds marathon pace more evenly.
The runner then tests the plan again in warm conditions. If nausea is reduced, the likely issue was cumulative carbohydrate, fluid, and effort rather than the gel alone. If symptoms remain, the runner can test a different product or lower caffeine exposure without changing every variable at once.
Final Takeaway
When Maurten gels make you nauseous at mile 18, troubleshoot the whole system: gel concentration, carbohydrate per hour, water, caffeine, heat, breakfast, and pace. Start with the least disruptive changes: follow the product directions, avoid large fluid boluses, fuel before exhaustion, and keep effort controlled.
Your race plan should be the version you have already tested successfully. The best marathon fueling strategy is not the most aggressive one. It is the plan that supplies enough carbohydrate and fluid while keeping your stomach calm.
FAQs
Should you take Maurten Gel 100 with water during a marathon?
Yes, taking Maurten Gel 100 near a water station can be a sensible option, especially if you are prone to nausea or take the gel without other fluid. Follow the package directions and avoid swallowing a gel immediately before a hard hill or surge. You do not need to force a large volume of water all at once. Practice the same timing, cup size, and drinking pattern during long runs so race-day conditions feel familiar.
Why do Maurten gels cause nausea late in a long run but not early?
Late-run nausea often reflects cumulative stress rather than one isolated gel. By mile 18, carbohydrate and fluid intake have built up, stomach movement may be slower, and marathon effort or heat may be higher. Review everything consumed during the previous two hours, including sports drink and caffeine. Test smaller doses, more spacing, steadier pacing, and measured water intake. If symptoms still occur at easy intensity or outside running, seek professional advice instead of continuing to experiment.
How many Maurten gels should you take per hour in a marathon?
There is no single correct number because Maurten gels contain different amounts of carbohydrate and runners tolerate different intake levels. Calculate grams of carbohydrate per hour from gels, drinks, and chews rather than counting packets. Many runners begin in the broad range of 30 to 60 grams per hour and build tolerance gradually, while higher targets require specific practice. Use the lowest amount that supports your run without causing stomach symptoms, then test it repeatedly before race day.
Can a caffeinated Maurten gel cause nausea at mile 18?
Yes, a caffeinated Maurten gel can contribute to nausea in runners who are sensitive to caffeine or who combine it with coffee, energy drinks, or multiple caffeinated gels. Caffeine may also make some people feel shaky or increase reflux. Track total caffeine, not just the final gel. Test the exact dose during a long run at marathon effort. If symptoms improve when caffeine is removed while other variables stay the same, use a non-caffeinated plan or discuss caffeine tolerance with a qualified professional.
Should you switch from Maurten gels after vomiting during a marathon?
Not necessarily, because vomiting can result from excessive pace, heat, dehydration, concentrated fuel, too much fluid, illness, or a product mismatch. First review the full pattern and stop using any plan that repeatedly causes symptoms. Do not test a completely new gel during race week. If you try another product, compare it in training under similar conditions and change only one major variable. Repeated vomiting, severe weakness, confusion, or heat-related symptoms require prompt medical attention.
How can you test a marathon gel plan safely before race day?
Test the plan during long runs, not for the first time in the marathon. Use the same breakfast, gel type, caffeine amount, approximate timing, water pattern, and target pace you expect to use in the race. Start with controlled conditions, then repeat the plan in warmer weather or on a similar course. Change one variable per test and record symptoms from the first gel onward. Finish your final meaningful experiment before race week so your race-day strategy remains familiar.