You've put in the training miles. You've dialed your pace. But if you hit mile 18 of a marathon with nothing left in the tank, none of that matters. Race-day fueling is one of the most important — and most overlooked — parts of preparation.
Energy gels are the simplest, most portable way to keep your glycogen stores topped off during a race. But with dozens of options on the market, picking the right one can feel overwhelming. This guide breaks down the top gels for race day, when to take them, and how many you actually need.
Why You Need Gels on Race Day
Your body stores roughly 90 minutes of glycogen — the fuel your muscles burn during sustained effort. Once those stores run out, you hit "the wall." Energy gels deliver fast-absorbing carbohydrates (typically 20–45g per packet) to delay or prevent that crash.
For races lasting longer than 60–75 minutes, gels aren't optional — they're essential. Even for shorter races like a fast 10K, a single gel 15 minutes before the gun can give you a noticeable boost.
How Many Gels Do You Need? A Distance Guide
One of the most common race-day mistakes is carrying too few gels — or forgetting them entirely. Here's a quick reference:
| Race Distance | Estimated Time | Gels Needed | When to Take |
|---|---|---|---|
| 5K | 15–35 min | 0–1 | Optional: 1 gel 15 min before start |
| 10K | 35–70 min | 0–1 | 1 gel 15 min before start if over 50 min |
| Half Marathon | 1:20–2:30 | 2–3 | 1 before start, then every 45 min |
| Marathon | 2:45–5:30+ | 4–6 | 1 before start, then every 30–45 min |
| Ultra (50K+) | 5+ hours | 8+ | Every 30–45 min, mix with real food |
Pro tip: Startly's race-day checklist automatically calculates how many gels to pack based on your expected finish time and preferred fueling interval. One less thing to think about on race morning.
The Best Energy Gels for Race Day
We've tested these gels across training runs and race days. Here are our top picks, organized by what matters most to runners.
Best All-Around: GU Energy Gel
GU has been the go-to gel for runners for over two decades, and for good reason. Each packet delivers 100 calories and 20mg of caffeine (in most flavors), with a smooth, syrupy consistency that goes down easily at pace. The flavor range is massive — from Salted Caramel to Jet Blackberry — so you're bound to find something you like.
At around $1.30 per gel, GU is also one of the most affordable options. It's the gel we recommend to first-time marathoners who aren't sure where to start.
Best for Sensitive Stomachs: Maurten Gel 100
If gels have ever given you GI distress mid-race, Maurten is worth every penny. Their hydrogel technology encapsulates carbohydrates so they pass through your stomach faster and with less irritation. The taste is intentionally neutral — almost flavorless — which some runners love and others find bland.
At 25g of carbs per packet and zero added flavoring, Maurten Gel 100 is the choice for runners who prioritize function over flavor. It's what many elite marathoners use on race day.
Best Natural Option: Huma Gel
Huma uses real fruit (chia seeds included) to deliver 22g of carbs per pouch. If you prefer whole-food ingredients over lab-engineered formulas, Huma feels like a step in the right direction. The texture is slightly thicker than GU — more like a fruit purée — and the flavors taste genuinely good.
The chia seeds add a small amount of omega-3s and fiber, though the primary benefit is still fast carbohydrates. Great for runners who want a more natural fueling option without sacrificing convenience.
Best Budget Pick: Clif Shot
Clif Shot delivers 24g of carbs with organic ingredients at a price point that's hard to beat. The consistency is thinner than most gels, making it easy to take without water. Flavors like Mocha (with 50mg caffeine) and Citrus are crowd favorites.
If you're training for a marathon and going through a lot of gels each week, Clif Shot keeps costs manageable without compromising on quality. A solid everyday and race-day option.
Best for Long Races: Maurten Gel 160
The Gel 160 is Maurten's higher-calorie option, packing 40g of carbs into a single packet. For marathon and ultra runners who want to minimize the number of gels they carry, the 160 is a game-changer. Two of these deliver the same carbs as three standard gels.
The packet is slightly larger, but the hydrogel formula keeps it easy on the stomach even at higher concentrations. If you're chasing a marathon PR and want maximum fuel with minimum fuss, this is the one.
Best Real-Food Alternative: Spring Energy
Spring Energy takes a completely different approach — their gels are made from real food ingredients like rice, fruit, and honey. The Awesome Sauce flavor (45g carbs) tastes like actual food, which is a welcome change deep into a long race when sweet gels start to feel nauseating.
The trade-off is that Spring gels are thicker and heavier than traditional options. But for ultra runners and anyone who struggles with highly processed fuel, Spring Energy is a revelation.
Quick Comparison
| Gel | Carbs | Caffeine | Best For | Price (per gel) |
|---|---|---|---|---|
| GU Energy | 20g | 20mg | All-around use | ~$1.30 |
| Maurten 100 | 25g | 0mg | Sensitive stomachs | ~$3.50 |
| Huma Gel | 22g | 0–25mg | Natural ingredients | ~$2.00 |
| Clif Shot | 24g | 0–50mg | Budget-friendly | ~$1.20 |
| Maurten 160 | 40g | 0mg | Long races, max fuel | ~$4.00 |
| Spring Energy | 30–45g | 0mg | Real-food fuel | ~$3.75 |
Race-Day Gel Timing Strategy
Having the right gels is only half the equation. Taking them at the right time is just as important.
Before the Race
Take one gel about 15 minutes before the start. This tops off your glycogen stores without sitting heavy in your stomach. Avoid taking one right at the gun — you want it absorbed before you start running hard.
During the Race
Set a fueling interval of every 30–45 minutes. The exact timing depends on your pace and how your stomach handles fuel at effort. Most runners find 45-minute intervals work well for half marathons, while marathon runners benefit from tighter 30-minute windows.
Always take gels with water, not sports drink. Combining a gel with sports drink creates an overly concentrated sugar solution that can cause cramping and nausea. If you know a water station is coming up at mile 6, plan to take your gel at mile 5.5.
The Golden Rule
Never try a new gel on race day. Always test your fuel during training runs. What tastes great at home can turn your stomach at race pace. Use your long runs to rehearse your exact fueling plan — same gels, same timing, same water intake.
Startly's Race Day Mode lets you set fueling reminders at custom intervals, so you'll get a gentle notification when it's time to take your next gel. No more mental math at mile 20.
How to Carry Gels During a Race
Where you stash your gels matters more than you think. Fumbling with a gel at pace wastes time and energy.
- Shorts pocket: Most running shorts have a small back pocket or side pocket. Good for 1–2 gels.
- Race belt / FlipBelt: The best option for 3+ gels. Distributes weight evenly and keeps everything accessible.
- Pin to your bib: Some runners use safety pins to attach gel packets to their race bib or shorts waistband.
- Handheld bottle with pocket: Many handheld bottles have a small zippered pouch — perfect for a couple of gels.
Whatever method you choose, practice it in training. You should be able to open and consume a gel with one hand without breaking stride.
Pack Your Race Bag the Night Before
The worst feeling is standing in a starting corral and realizing your gels are sitting on the kitchen counter. Add your gels to your race bag checklist the night before — along with your bib, timing chip, and everything else you need.
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