You’re standing at the start line of a marathon, race belt packed with gels. But how many should you actually eat? Take too few and you hit the wall. Take too many and you’re dealing with stomach cramps. This article gives you the exact numbers, timing, and strategy for gel consumption based on exercise science and what works in practice. The question of "how many gels during a marathon" is really about meeting your carb needs without overdoing it.
Quick Answer
Aim for 60 to 90 grams of carbohydrates per hour during the marathon. For a standard gel with 20–30 grams of carbs, that means 2 to 3 gels per hour.
- Start taking your first gel 45 to 60 minutes into the race, not before. Your body still has stored glycogen at the start.
- After that, take one gel every 20 to 30 minutes.
- For a 4‑hour marathon that’s roughly 6 to 9 gels total.
- Wash down each gel with a few sips of water (not sports drink, unless you account for the extra carbs).
This sounds like a lot, but it matches the maximum amount of carbs your gut can absorb per hour. If you’re a slower runner or run in hot conditions, stay closer to 60 g/hr. If you’re aiming for a fast time and your stomach tolerates it, push toward 90 g/hr.
Why This Happens
Your muscles store about 1,800–2,000 calories of glycogen, enough for roughly 18–20 miles at a hard pace. After that, glycogen runs low and your body becomes less efficient at burning fat for the pace required. That’s when you “hit the wall.”
Exogenous carbohydrates (from gels) delay that point. The small intestine can absorb about 60 grams of glucose per hour, but if a gel contains a mix of glucose and fructose, absorption can go up to 90 g/hr because they use different transport pathways. That’s why many gels now use a dual‑source carb blend.
If you take fewer than 60 g/hr, you’re leaving performance on the table. If you take more than 90 g/hr, the extra sits in your gut and causes bloating or diarrhea. The “2–3 gels per hour” rule is a practical translation of that science.
Step-by-Step Method
Follow these ordered steps to dial in your marathon gel strategy:
1. Calculate your carb target per hour.
- Faster runners (sub‑3:30) → 80–90 g/hr
- Mid‑pace runners (3:30–4:30) → 60–80 g/hr
- Slower or heavier runners (over 4:30) → 50–60 g/hr (gut tolerance often lower)
2. Pick your gel. Look at the label. Most gels list carbs per serving (20–30 g). Some “double” gels have 40 g. Divide your hourly target by the gel’s carb amount to get gels per hour.
3. Map the timing.
- First gel at mile 5–7 (about 45–60 minutes).
- Then repeat every 20–30 minutes.
- For a 4‑hour plan: gel at 0:45, 1:15, 1:45, 2:15, 2:45, 3:15. That’s 6 gels, roughly 120–180 g total depending on gel size.
4. Drink water with each gel. Carb solutions must be diluted to be absorbed. A gel without water pulls fluid into your gut and can cause cramps. Aim for 4–6 oz of water per gel.
5. Practice in training. Never try a new gel or schedule on race day. Do at least 3 long runs with your planned routine. Adjust based on how your stomach feels.
6. Adapt for conditions. Heat slows gastric emptying. On a hot day, drop to 60 g/hr max and increase water. On a downhill course, you might tolerate more.
Common Mistakes
Mistake 1: Starting gels too early. Taking a gel at the start line or in the first 30 minutes is unnecessary. Your glycogen stores are full, and early carbs don’t boost performance. Wait until mile 5–7.
Mistake 2: Taking two gels at once to “catch up.” Your gut can only process so much at a time. Doubling up increases the risk of GI distress. Stick to one gel every 20–30 minutes.
Mistake 3: Not drinking enough water. Gels are concentrated. Without water, they’re hard to digest and can cause nausea. Use water, not sports drink, unless you’ve practiced with a specific product.
Mistake 4: Ignoring sodium. Many gels contain sodium, but on a hot day you may need extra electrolytes. If you’re a heavy sweater, consider a salt tablet or an electrolyte drink alongside gels.
Mistake 5: Using unfamiliar gels on race day. The sample pack from the expo might seem like a good idea, but a new texture, flavor, or ingredient can wreck your race. Stick to what you trained with.
Checklist or Decision Table
Gel Brand Comparison (approximate values per gel)
| Brand | Carbs (g) | Caffeine | Sodium (mg) | Best For |
|---|---|---|---|---|
| Maurten Gel 100 | 25 | No | 10 | Sensitive stomach, dual‑source carbs |
| GU Roctane Energy Gel | 26 | Yes (35 mg) | 60 | Extra energy boost, longer events |
| Clif Shot | 25 | No | 50 | Natural ingredients, budget‑friendly |
| Science in Sport (SiS) Go Gel | 22 | No | 86 | Light texture, easy to swallow |
| Honey Stinger | 21 | No | 40 | Honey‑based, gentle on stomach |
| Spring Energy Awesome Sauce | 25 | No | 10 | Whole food base, real fruit |
Race Day Checklist
- Gels packed in belt or pockets (one more than planned for emergency)
- Water bottle or plan for aid stations
- Tested gel schedule during at least one long run
- Extra gel taped to shorts or wrist for backup
- Know where aid stations are (water stops)
- Have a backup plan if stomach turns (switch to plain water + salt for a while)
When This Advice Does Not Apply
This 60–90 g/hr guideline is for runners who rely on carbohydrate fueling and have a healthy GI tract. It does not apply if:
- You follow a keto or low‑carb diet and are fat‑adapted. In that case you may need far fewer gels or none at all, but you must have practiced that way extensively.
- You have diabetes or blood‑sugar issues. Gels can spike glucose; consult a doctor or sports dietitian for a tailored plan.
- You have a history of severe GI problems like IBS. Start with a lower carb dose (40 g/hr) and test gut tolerance.
- You are running a shorter race (half marathon or less). For runs under 90 minutes, a gel may not be necessary, especially if you’ve eaten beforehand.
- You are a heavy sweater losing lots of sodium. In that case, electrolyte balance matters as much as carbs. Use gels with higher sodium or supplement.
Realistic Example
Runner profile: Sarah, age 34, aiming for a 4:00 marathon. She practices fueling on her long runs. She chooses Maurten Gel 100 (25 g carbs each). Her target is 60 g/hr (moderate pace). That’s 2.4 gels per hour, so she rounds to 2 per hour for simplicity, taking one extra to be safe.
Her plan: Gel 1 at mile 6 (~50 min), Gel 2 at mile 10 (~1:25), Gel 3 at mile 14 (~2:00), Gel 4 at mile 18 (~2:35), Gel 5 at mile 22 (~3:10). That’s 5 gels total, 125 g carbs = about 31 g/hr average over 4 hours. She also drinks water at every aid station. During her longest training run (20 miles), she practiced this schedule and felt great. On race day she carries 6 gels (one extra in case of drop). She finishes 3:57 and didn’t hit the wall.
Final Takeaway
Don’t guess your gel intake. Use the 60–90 g/hr target, divide by your gel’s carb content, and schedule one gel every 20–30 minutes starting after 45 minutes. Practice the exact plan on long runs. If it works, stick with it. If you get GI trouble, dial back on both carbs and water until you find your sweet spot. The right number of gels isn’t a fixed count—it’s the amount that keeps you energized without upsetting your stomach.
FAQs
How many gels do I need for a 4-hour marathon?
For a 4-hour marathon, aim for 6 to 8 gels total, depending on the carb content per gel. If each gel has 25 g carbs, 6 gels provide 150 g total, which averages about 37.5 g per hour. That’s a bit low. Try 8 gels (200 g total, 50 g/hr) if your stomach can handle it. Always test during long runs first.
Is it better to take gels with or without water?
Always take gels with a few sips of plain water. The concentrated sugar needs to be diluted to be absorbed properly. Water also helps prevent the gel from sticking in your mouth. Avoid sports drinks with gels unless you’ve practiced with that combination, because the extra carbs can overload your gut.
Can I eat too many gels during a marathon?
Yes. Eating more than 90 grams of carbs per hour can cause nausea, bloating, diarrhea, or vomiting. The gut has a finite absorption rate. Too many gels also risk a sugar overload that leads to a crash later. Stick to the 60–90 g/hr range and adjust downward if you feel sloshy or uncomfortable.
When should I take my first gel in a marathon?
Take your first gel about 45 to 60 minutes into the race (typically around mile 5 to 7). Your body still has plenty of stored glycogen at the start. Starting earlier doesn’t help and may cause GI issues. If you are a slower runner, you can wait until 60 minutes.
Do I need different gels for hot weather?
Yes. In hot weather, blood flow shifts to the skin for cooling, reducing blood flow to the gut. This slows digestion and increases the risk of GI problems. Drop your carb intake to about 50–60 g/hr (2 standard gels) and increase water intake. Also choose gels with higher sodium content or add electrolyte tablets to your water.
What if I don’t like the taste or texture of gels?
You have alternatives: chewable blocks, sports beans, dried fruit, or even homemade fuel like diluted honey. The key is still getting 60–90 g carbs per hour. Test several options during training. Many runners also use a mix of gels and real food (like bananas or dates) as long as it’s easy to carry and digest on the run.