Running a marathon without training — or at least without enough training — is more common than you might think. If you’re feeling undertrained or underprepared for your upcoming marathon, these tips will help you get through race day.
You’re not alone. For many novice and amateur runners, the final weeks before race day can bring a wave of nerves, second-guessing, and “what if” thoughts. Missed long runs, interrupted training blocks, or workouts that didn’t go as planned can suddenly feel much bigger as the start line approaches.
If you’re starting to panic and wondering how you’re going to make it through 26.2 miles, take a breath. Even if your preparation wasn’t perfect, there are smart, practical strategies you can use to get to the finish line strong. When training falls short, execution matters even more.
Running a marathon underprepared isn’t about chasing a bold time goal. It’s about conserving energy, managing effort, fueling wisely, and making disciplined decisions from the first mile to the last. As the saying goes, it’s a marathon, not a sprint.
Think of this as your race-day survival guide, whether it’s your first marathon or your buildup didn’t unfold the way you hoped. With the right mindset and pacing strategy, you can navigate the highs and lows, cross the finish line, and maybe even surprise yourself along the way.
#1: Fuel Smart Pre-Race
The overarching theme of this whole piece is the art of saving energy.
Your body loves to run on glucose. It’s your primary fuel source during a race, and what your muscles rely on most. Glucose is a form of energy derived from sugars and carbohydrates, and it’s stored in the body as glycogen.1Murray, B., & Rosenbloom, C. (2018). Fundamentals of Glycogen Metabolism for Coaches and Athletes. Nutrition Reviews, 76(4), 243–259. https://doi.org/10.1093/nutrit/nuy001
What makes it so valuable on race day is how quickly your body can access it—it’s fast-release, meaning it’s ready to go almost immediately when you need a boost.
You’ve probably heard runners talk about “carb loading” before a big race. That’s essentially the strategy of topping off your glycogen stores, so you’re as full of quick-access fuel as possible come race morning.
The more glycogen you have in the tank, the longer you can keep moving smoothly and efficiently.
But once those stores start to run low, your body shifts gears and begins burning fat for energy. That’s when things can get a bit rough. Fat is a much slower and less efficient energy source—so you start to feel sluggish, heavy-legged, and drained.
That’s also when runners hit what we call “the wall” or experience a full-on bonk. Trust me, bonking is no joke—it’s that point where your legs feel like lead and even walking feels like a major effort.
If you’re heading into a marathon in survival mode, especially if your training didn’t go exactly to plan and you’re aiming to simply get through it, managing your glycogen is key.
The longer you can preserve those energy stores—by fueling well before and during the race—the better chance you have of making it to the finish line strong, or at least without completely falling apart.
How to Carb Load
Carb loading doesn’t mean eating an entire pizza the night before. In fact, most of the work happens 48–72 hours before race day, not just at the pre-race dinner.
#1. Increase Carbohydrates 2–3 Days Out
Aim for roughly 7–10 grams of carbohydrates per kilogram of body weight per day during the final two to three days before the race.
#2. Choose Lower-Fiber, Easily Digestible Carbs
In the final 24–36 hours, shift toward easy-on-the-gut carbohydrates to avoid race-morning GI issues.
Good options include white rice, pasta, potatoes, oatmeal, bagels or white bread, pancakes or waffles, pretzels, bananas, sports drinks, and low-fiber cereal.
Reduce heavy fiber, large salads, beans and legumes, greasy foods, and spicy foods.
The goal is to maximize glycogen without irritating your stomach.
#3. Keep Protein Moderate, Fat Lower
You don’t need to eliminate protein or fat; just don’t let them crowd out carbohydrates. Keep meals balanced but carb-dominant.
#4. Don’t “Stuff” Yourself
Carb loading is about increasing carb percentage, not overeating to the point of discomfort. Slight fullness is normal — feeling miserable is not.
#5. Race Morning: Top Off, Don’t Overdo It
Eat 2–3 hours before the start if possible. Aim for 1–3 grams of carbohydrate per kilogram of body weight.
Examples include a bagel with honey and a banana, oatmeal with maple syrup, toast with jam, or a sports drink for those who have trouble eating solid foods before racing.
Keep it familiar. Race morning is not the time for experimentation.
#2: Continue To Fuel During The Race
As well as stocking up on carbohydrates before the race, you will also need to stock your glycogen stores during the race.
Energy gels and sports drinks contain high levels of it in an easy-to-digest way.
The key is to fuel early, consistently, and in the right amounts.
Aim to take in 30–90 grams of carbohydrates per hour — ideally starting within the first 30–45 minutes of the race. This can come from energy gels, chews, sports drinks, or even real food like bananas or small bites of granola or chocolate bars (if your stomach can handle them).
Try spacing your fuel intake every 20-30 minutes to avoid overloading your stomach and risking cramps or GI issues. During any walk breaks, use that time to sip or nibble — it’s often easier to digest fuel when your body isn’t bouncing around at full speed.
Also, don’t forget hydration. Sports drinks can be a great way to get both carbs and electrolytes, but be mindful of how much you’re taking in — the amount will depend on temperature, sweat rate, and your individual needs.
If you’re looking for a full breakdown of what to eat before, during, and after your race, check out our complete marathon nutrition guide.
#3: Use The Run/Walk Technique
A great way to keep your energy levels high is to go slow.
The run/walk technique is a great way of keeping your pace manageable while also giving your body lots of energy-saving walk breaks throughout the marathon.
You will often see ultra runners using the same technique to cover the massive distances of an ultramarathon. If it works for them, it will work for you.
Break up your marathon into 1-mile walking sections and 4-mile running sections.
The chances are that you will be capable of running the first 4 miles (1 mile is approx 1.6km) without much of a sweat. Then, give yourself a walk break for a mile. Then run 4 miles, walk 1 mile, and so on.
Each time you walk, you will lose around 5-10 minutes for that mile, but it will be much more time-efficient than lying in a bush with a DNF waiting for someone to pick you up.
The important thing to remember is that you are in the race for the long game. The first break may seem too easy, but be patient – remember there are over 20 miles to go. So, walk the whole mile, nice and steady, and don’t overdo it.
You will not win the marathon with this technique, but we are here to finish, don’t worry about your time.
#4: Forget about Finishing Times
The clock at the finish line can be the downfall of so many runners — I’ve seen it happen time and time again. When you’re undertrained or just trying to make it through the race, your goal shouldn’t be a specific time; it should be to finish strong and injury-free.
Sure, elite athletes are chasing the podium positions, but for most of us, the real competition is ourselves — not the clock. That’s a mindset shift that can be hard, especially if you’re naturally competitive. But trust me, it’s one of the most important lessons to learn.
One of the biggest traps I see runners fall into — both first-timers and veterans — is getting pulled along by others’ pace.
Countless runners let their ego take the lead early in the race, only to crash hard halfway through. They go out too fast, and by mile 10 or 11, they’re clinging on for dear life. In the end, they’d have been better off sticking to their race plan, running their pace, and tuning out the noise.
So when someone passes you, give a friendly nod or a “hello” — then let them go. Stay focused on your own path, your own rhythm. The finish line will still be there, and it’ll feel a whole lot better when you cross it on your terms.
#5: Use The Rate Of Perceived Exertion (RPE)
RPE, or Rate of Perceived Exertion, is simply how hard an activity feels to you on a scale of 1 to 10. A short, all-out sprint might feel like a 10 — maximal effort, where you’re gasping for air — while an easy walk might feel like a 1 or 2 — completely relaxed and effortless.
During a marathon, your goal is to keep your RPE on the lower end of the scale, especially in the early miles. Ideally, you want to sit around a 4–5 out of 10. That should feel like a steady, manageable effort — you’re working, but you could comfortably carry on a conversation.
If you start creeping up into a 6-7 range too soon, that’s your cue to ease up. Take a walk break if needed, reset your rhythm, and return to a more sustainable pace. High RPE too early almost always leads to burnout later in the race.
Numbers aside, the most important thing is to listen to your body. Stay relaxed, check in with how you’re feeling, and let that be your guide. Your perceived effort is one of the most reliable tools you have on race day — no watch or gadget required.
#6: Enjoy it!
Enjoyment may seem like an odd one to include here, but it plays a very important role in your run. It’s normal for marathons to be physically and mentally straining, so try to run in a way that prioritizes your enjoyment.
This will not only protect your mood, but actually causes physiological changes that will help you complete your run. Good-mood endorphins like oxytocin are released when you’re happy and smiling – and these endorphins are linked to improved stamina and performance.2Pepping, G.-J., & Timmermans, E. J. (2012). Oxytocin and the Biopsychology of Performance in Team Sports. The Scientific World Journal, 2012, 1–10. https://doi.org/10.1100/2012/567363
Even if you are completely out of energy and your running shoes feel heavier than bricks, you can always take more walk breaks. Lots of people walk a marathon (as long as the cutoff time allows). Remember, it’s the distance that is the challenge, not the time.
Just keep going and keep smiling. You can do it!
Now, maybe this time you can get away with finishing the marathon without ideal preparation. Grit can carry you a long way. But let’s be honest, running a marathon is a whole lot more enjoyable when you show up confident, strong, and properly trained.
Instead of surviving the miles, you get to race them. Instead of counting down the distance, you get to lean into it.
To make sure you toe the line feeling prepared next time, check out our database of free marathon training plans, designed for different experience levels, goals, and timeframes.
And if you’re ready for something even more tailored, we also offer one-on-one personalized coaching, where your training is built specifically around your schedule, strengths, weaknesses, and race goals.
Because finishing is great. But finishing strong — and actually enjoying the journey — is even better.
