DNF Guide: Why Runners DNF, Prevention, and Tough Decisions

What to do to avoid a "do not finish" at all costs.

DNF. I’m sure you’ve seen those dreaded letters at the end of a race results list, more often than not, in longer races such as ultramarathons or stage races.

Let’s be honest: deciding to pull out of a race you have trained months and months for is every runner’s worst nightmare and one of the most difficult decisions to make.

What Does DNF Stand For?

Did not finish. 

You may have also seen DNS, did not start, or DQ disqualified. 

Yes, they aren’t ideal situations and the hope is you’ll never experience any of them, but if you do, it’s important to know it’s not the end of the world. 

We just brush ourselves off, get up, and go again! 

Talk to any runner that’s been doing events long enough and you’ll find they have at least one DNF to their name.

DNF Guide: Causes, Prevention and Tough Decisions

When To DNF From A Race

Contrary to popular belief, there is no shame in a DNF, and at some point or another during your running career, you are most likely going to have to face making that tough decision. 

There will be some instances where a DNF is absolutely necessary, and it’s important to know that it’s okay to do it under certain circumstances. 

Sometimes, the decision is made for us; sometimes, we need to make that decision ourselves, and sometimes, we need to get ourselves back in check and differentiate between wanting to DNF because we don’t feel like running and having to DNF because of an uncontrollable issue. 

A DNF can often be prevented or avoided, but it’s important to know when to call it.

When Should You DNF?

If you . . .

  • have a serious accident on the course and are left injured,
  • feel unsafe because of failed equipment or an unexpected change in weather,
  • or your body is not responding as it should due to any number of health issues,

you should strongly consider abandoning the race as soon and as safely as possible.  

Even if you haven’t been in an accident but feel pain that you know isn’t just tired legs, it’s better to avoid making your injury worse and risk a long, painful recovery and leave the race.

Under any of these circumstances, it’s best for you to make that difficult decision and take a DNF.

DNF Guide: Causes, Prevention and Tough Decisions

When Should You NOT DNF?

You never want to DNF because the race just isn’t going your way or you don’t feel like finishing. 

If you find yourself having these thoughts, reset your mindset.

Racing isn’t always about getting a PR or reaching a specific time goal that you have set for yourself.

If you’re running and realize you won’t finish in the planned time, instead of giving up, slow your pace down, relax, and change your goal. Races are unpredictable, and it’s always good to have a plan A, B, and maybe even C, just in case.

Decide to enjoy the rest of the race. Begin to think of it as just another long run with fun aid stations and a helpful crew along the way.

One risk of DNFing without sound reason is that it may become a habit. Once you’ve done it the first time, it becomes easier and easier to call it quits.  

You’re a runner; you’re stronger than that. You’ve trained hard. Push those negative thoughts aside, and do this

Knowing that you were tough enough to persevere and achieve your goal against all odds makes it even more memorable.

Now, let’s examine some of the most common causes of DNF and how we can do our best to prevent them.

7 Common DNF Causes and Prevention Tips

As runners, we know that there are endless uncontrollable factors that can hurt the outcome of our race. That being said, rule #1 is to control what we can and fix what breaks along the way to the best of our ability.

#1: Accidents on the Course

You’re prepared, feeling great, and out of nowhere, you take a spill on some loose rocks, twist an ankle on a hidden root, or simply get tangled up in your own feet.

Most of the time, you’ll bounce right back from these common slips and falls, but if you are truly hurt, there is no reason to keep going and worsen the injury.

Assess your fall and decide whether it’s just a bump or a potential injury.

Then, make the call.

DNF Guide: Causes, Prevention and Tough Decisions

How to Prevent Accidents

Being strong and well-trained will give you a fighting chance against tough terrain and a spill every now and then. 

Strength training is essential to keep runners strong and injury-free. 

In addition to strengthening your joints and muscles, it also improves your mobility, coordination, agility, and flexibility. 

This means you’ll be able to dodge that root you saw at the last minute or anticipate a potentially hard fall and readjust your footing just in the knick of time.

#2: Lack of Fueling

If you stop giving your body the energy it needs to overcome this challenge, you risk hitting the wall. Once you hit that wall, it’s very difficult to make a comeback.

Without energy, there is no way your body will be able to continue pushing.

How to Prevent Hitting the Wall

A well-designed and heavily practiced nutrition plan is crucial for a successful race. 

Be sure and calculate your specific nutritional needs to be fully aware of exactly how many carbohydrates you will need to consume per hour. If you don’t have a nutritionist, try out the following formula to get a general idea: 

Weight in kilos = grams of carbs per hour you need to consume 

After calculating how much you’ll need, try out different types of products until you find what works best for you. You can mix and match gels, bars, chews, and carbohydrate-filled energy drinks; just ensure you reach your hourly goal.  

If you have trouble keeping track of your intake, set alarms on your watch to remind you every time you need to eat. 

We can practice our nutritional plan a million times, but sometimes, it becomes impossible to get anything down at a race. In this case, eat what appeals to you, and just make sure you are fueling!

DNF Guide: Causes, Prevention and Tough Decisions

#3: Dehydration

Hydration is equally important as nutrition. Some may think dehydration is only a risk in hot-weather races, but it is a potential issue in all races. 

When we run races in cooler climates, we don’t pay as much attention to our hydration needs because we simply don’t feel thirsty. You need to consistently replace what your body is using because if you don’t, dehydration can put you on a dangerous path to a DNF. 

Here are some signs of dehydration to look out for:

  • Dry mouth
  • Extreme thirst
  • Fatigue
  • Dizziness
  • Cramping
  • Dark-colored urine

If you are experiencing these symptoms, try to hydrate and stop at the next aid station for help. 

DNF Guide: Causes, Prevention and Tough Decisions

How to Prevent Dehydration

You never want to reach the stage of feeling any dehydration symptoms because once you get there, it may be a little too late to recuperate. 

As you did with your nutrition, your hydration should be well-practiced in your long runs and down to a science.

At the beginning of your training season, you should take a sweat test to determine how much you actually sweat per hour. Be sure to do the test in a climate similar to that of your race so your results will be more accurate.

Sweat Test

  1. Weigh yourself without clothes or shoes before you run. 
  1. Run for one hour at race pace. This will vary greatly depending on the distance of your race. If it’s a 5K, you’ll probably run at a much harder effort than if you are going for a 100-miler. 

Important! Do not consume or get rid of any liquid during the run…. In simpler terms, no drinking or peeing! If you do, you’ll have to measure it to either add it or subtract it from your total. 

  1. After you have completed the hour run, take off your shoes and clothes, towel off, and weigh yourself again
  1. Now, calculate! 

Pre-run weight – post-run weight = milliliters (or ounces) used per hour. 

Replenishing 100% of this liquid is quite a feat, but do your best to stay as hydrated as possible!

#4: Feet

We need our feet in tip-top shape to run. Hot spots, blisters, and toenail damage are all issues that most runners deal with at one point or another. 

Unfortunately, these issues can be detrimental to the outcome of a race, especially when running an ultra distance.

It’s easier to tolerate something for a few kilometers, but hours and hours with a blister covering your entire heel will become unbearable.

DNF Guide: Causes, Prevention and Tough Decisions

How to Prevent Foot Issues

Our feet are our prized possessions, so we need to take great care of them not only when racing . . . but all the time.

Here are some general tips to keep those feet in tip-top shape:

Get a Pedicure

If you want to do it yourself, by all means, but be sure and:

  • Hydrate feet with lotion
  • File down calluses 
  • Keep nails short and clean

Choose the Right Running Sneakers and Socks

Be sure to choose sneakers that fit correctly so there is no uncomfortable rubbing or friction.

Especially when running trail, you need to have space in the toe box so you can comfortably run downhill without banging your toes against the inside of the shoe. This could lead to losing a toenail mid-race. 

Socks come in all shapes, sizes, materials, styles, lengths, and thicknesses. Try out different brands and types to see what works best for.

Foot Care During a Race

Applying diaper cream on your feet can help immensely avoid friction and blisters. It works much better than Vaseline as it doesn’t absorb or rub off into your socks as quickly. 

You are usually allowed to have a drop bag in ultras, so leave a bit of extra cream in there along with another pair of socks, just in case you’d like to change them halfway through the race.

You can also leave another pair of sneakers in case the ones you are using start to bother you. 

If you feel something in your shoes during the race, stop and fix it immediately. It could simply be a bunched up sock or a rock that snuck in there. if you leave it, it will cause hot spots, which can turn into painful blisters.

It’s worth taking a minute to fix the issue so it doesn’t turn into something that could cause you to drop out.  

Foot care is probably the most neglected area of distance running.

To help avoid getting anything into your shoes, you could try using gaiters. These are especially helpful for races where there is a lot of sand or loose terrain.

DNF Guide: Causes, Prevention and Tough Decisions

#5: Cutoffs

Most ultra races have several pre-established cut-off times throughout the race for the runners’ safety. This is a DNF that would not be voluntary; here the decision is made for you.

In every race there are runners who show up unprepared and undertrained. They try to take on the challenge they are not quite ready for and may be setting themselves up for failure.

How to Beat the Cutoffs

Be Prepared

Being fully prepared and well-trained for a race can diminish your chances of not making a cut off time substantially.

It’s important to take your training seriously by following a professional training plan specific to your race and fitness level, eating and sleeping well, strength training, and respecting your rest days. 

Study your Race

You don’t want to go into a race blindly, not knowing what to expect. Most races have ample information available for you to study beforehand

Research the location of the race, the weather during the time of year it takes place, and the types of terrain you will encounter. Doing some of your long runs in similar conditions makes for a great race simulation. 

Also, be aware of the cut-off times and checkpoints so there are no unpleasant surprises. This way, you will know how to pace yourself and arrive at each aid station with plenty of time to spare.

Don’t Overtrain

The extreme of showing up underprepared is showing up overtrained.

This fatigue can take over and completely sabotage a race. Rest days and taper weeks need to be respected. A common misconception is that more is better, but that is not the case. Be sure you don’t overdo it before the race so you can show up well-rested and raring to go!

Control Your Pace

Your adrenaline will be pumping at the start line, and you’ll want to begin the race like a horse out of the gate.

But think about all the kilometers you have to go. Start out at your planned pace, don’t follow the crowd and go out too hard. If you do, you’ll most likely end up burning out. 

You’ve done all of your long runs to simulate the real deal, so put those lessons into practice on race day. Towards the end, if you have the energy, finish strong!

Negative splits are something to brag about!

#6: Your Mind Fails You

We have a lot of time to think while racing, especially in ultras, and our minds spin round and round and can sometimes go to dark places.

Quitting is a thought that pops up every now and again, but in this case, it’s just your mind, you just don’t feel like going anymore.

DNF Guide: Causes, Prevention and Tough Decisions

How to Beat Your Mind

There are different ways of dealing with ups and downs during a race, but here are some tips to help you push through. 

Think Happy Thoughts

Think of the months and months of hard work you have put into this day and the happiness you’ll feel once you cross the finish line. Your family and friends will be bursting with pride, and you’ll have earned some pretty awesome bragging rights.

Look for Company

Try to find someone to talk to; a great conversation can make the time fly by.

Get Pumped Up

Take out your headphones and put on an upbeat playlist. Smile, laugh, sing aloud. Or repeat a helpful positive phrase over and over again to yourself.

You can do this; it’s all in your head.

DNF Guide: Causes, Prevention and Tough Decisions

#7: Weather

Weather is a factor that is often out of anyone’s control.

Mother Nature is in charge here and occasionally pushes the race director to call an event off because it’s too dangerous to continue.

It’s important to respect that decision because it benefits and protects everyone involved: runners, staff, and crew. 

However, if the weather is extreme but under controlled conditions, you don’t want to be caught unprepared.

How to Beat the Weather

Study your race’s climate in advance and bring all the clothing and equipment you may need.

If you are battling changing temperatures, bring layers, a waterproof jacket, gloves, a hat, or whatever you need to be comfortable.

There’s nothing worse than knowing your uncontrollable shivering could have been avoided if you had only brought the necessary equipment along.

DNF Guide: Causes, Prevention and Tough Decisions

If I Have To DNF, Then What?

Ok, you had to make that tough decision, but you know what, you’ll get through this. It’s okay to have a bad day.

Here are some wise words from marathoner and ultra runner Michael Wardian after his DNF at China’s 100-mile Mount Gaoligong Ultramarathon:

“The decision to quit was ridiculously hard as I felt like it was admitting that I am not a machine but human and have faults and can fail.”

So what do you do now?

Choose Your Next Goal

It is much easier said than done, but after being forced to DNF, try to move past it as quickly as possible instead of dwelling on something you can’t change.

Pick a new goal and make it an exciting one. It could even be coming back to the very same race next year and giving it another go! 

You’ll show that race whose boss!

DNF Guide: Causes, Prevention and Tough Decisions

Remember Why You Run

A very small percentage of us run for a living. Most of us run for fun.

Yes, we put months and months of training and effort into our races, and yes, sometimes it doesn’t go as planned. But there will be other races, other trips, other memories to be made. 

We can learn from our DNFs. As an ultramarathoner and running coach myself, I like to analyze difficult runs I have had, to figure out what went wrong and improve for next time. 

I hope this guide helps to prevent you from ever needing to DNF, but remember, if you need to, don’t be so hard on yourself.

You’ll get another shot. 

For a great information on fueling, check out this next guide:

Photo of author
Katelyn is an experienced ultra-marathoner and outdoor enthusiast with a passion for the trails. In the running community, she is known for her ear-to-ear smile, even under the toughest racing conditions. She is a UESCA-certified running coach and loves sharing her knowledge and experience to help people reach their goals and become the best runners they can be. Her biggest passion is to motivate others to hit the trails or road alongside her, have a blast, and run for fun!

2 thoughts on “DNF Guide: Why Runners DNF, Prevention, and Tough Decisions”

  1. Superb and exactly what I needed to read today after pulling out 2 miles in!! Yes a bit underfit as post viral but today was about my mental strength being under par… First dnf after many many long tough runs.. This was a 10k!! Reflecting on it, if it had been a half upwards I would not have pulled out but at THAT MOMENT, at the top (yup I had done the tough bit) I just couldn’t be bothered.. Maybe an arrogant disregard for a short distance, I don’t know (last one was a fantastic 33 miles) glad I pulled out as its given me a chance to reflect on where I am at but once is definitely enough 😂


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