How To Know If You Should DNF A Run

Experiencing a DNF in running, especially more than once, is inevitable. No runner is invincible – even elite runners – and sometimes a DNF can happen to you due to something that is out of your control.

But how do you know when to DNF? 

How To Know If You Should DNF A Run

There are numerous reasons why a DNF can and should be necessary. In fact, there is nothing wrong with having to DNF a run if you feel that it is the right decision. There is also no penalty for a DNF in running.

You might have experienced a DNF before or you might be someone who is looking to know when a DNF is acceptable.

Either way, this guide is going to help you understand more about DNFs and how to know if you should DNF a run.

What Is DNF In Running?

A DNF in running is an initialism that stands for “did not finish”. It is a term that is also used in other activities that are not fitness or sports-related.

Typically, in running, DNF is used to describe an organized running event that the runner was not able to finish (cross the finish line) due to one or several reasons, which can be personal or out of their control.

It is a term that is most common in long-distance/endurance running events, such as 10k runs, half marathons, marathons, and ultramarathons that are challenging to finish.

How To Know If You Should DNF A Run

So, how do you know if you should DNF a run?

There is more than one reason why you can and should DNF a run. In most cases, it will be your decision. But, in other cases, it might be due to something that is out of your control.

Whichever it is, there is no penalty in running for having to DNF. And no matter your personal reason for DNFing, all reasons are, and should be considered, perfectly acceptable.

Listed below are all the ways to know when you should DNF a run.

Pain And Injury

Pain and injury are obvious reasons you should DNF a run. Of course, there are different levels of pain and injury, and in general it’s up to you to decide when to stop running.

It’s better to be safe than sorry, so any pain and injury experienced while running should be assessed appropriately.

For example, a blister might not be considered serious in comparison to a stress fracture or tendonitis pain.

If something does not feel right, it’s better to stop – or at least walk until the pain is better evaluated. 

Additionally, if you feel that you are aggravating a past injury, the same applies. Exacerbating an injury or aggravating a past injury by continuing to run is not worth it and will ultimately set you back in the future.

Runner’s Wall

Runner’s wall is real and can happen to any runner, no matter their level of ability. It occurs when a runner hits a “wall”, in terms of their endurance, and can no longer continue to run.

To put it simply, runner’s wall happens as a result of a depletion of glycogen. Glycogen is a sugar that acts as a source of energy that, for all people, is finite.

And it can still deplete no matter how much you carb-load or eat during the race.

The end result is complete exhaustion and the inability to continue to power muscle contractions.

Your legs will feel incredibly heavy to move and may even lock up. In this case, a running DNF is unpreventable.


Danger is another big reason to DNF a run. In any organized running event, if the running course or weather conditions are considered too dangerous, it is better to stop running altogether.

In this case, the DNF would be out of your control. And examples of danger can include an unforeseen change in the route or terrain that is dangerous, or adverse weather conditions such as snow and ice, thunderstorms, storms or strong winds, and excessive heat.

If any of these put your safety at risk or prevent you from running altogether, it is best to DNF.

Lack Of Focus

Lack Of Focus

It isn’t always possible to bring your A game to every race. Life gets in the way and having a perfect mental state is not maintainable – even for the best runner or athlete.

If you are not focused on the race due to stress, a recent tragedy, or just not feeling good in general, there is nothing to stop you from DNFing the run.

It might be tempting to push yourself to keep going – and you should if you feel that you can continue – but, at the same time, it might lead to further frustration, injury (due to lack of focus and bad form), or simply DNFing later on, regardless. 

Shoe Degradation

If your shoes fall apart while running, this is another obvious reason you should DNF.

If you don’t have a spare pair of shoes that are suitable for you to continue, it is not worth running barefoot or even in shoes that do not fit or are not appropriate.

In general, this is something that would be out of your control. Still, it is avoidable by quality-checking your shoes before the race and bringing a spare pair of similar running shoes, just in case.

Continuing to run barefoot or in unsuitable shoes can lead to injury.

Missing The Cut-Off

Lastly, if you miss the cut-off time for any particular running event, this, unfortunately, is an instant DNF.

Most organized long-distance running events, such as marathons, have a cut-off time for reaching the finish line.

Cut-off times are not put in place to “cut off” the people who are not fit to finish the race, but simply because the event cannot continue all day.

You might miss the cut-off time due to injury, runner’s wall, a lack of focus, or another reason. In any case, this must be accepted as a DNF.

How To Get Over DNF

If you experience a DNF, how do you get over it?

Firstly, it’s important to remember that a DNF can happen to any runner – even elite athletes – not just once, but multiple times. And sometimes it is due to something that is not in your control.

Ultimately, the best thing to do is to consider DNFs as a learning experience to assess and build on. 

What went wrong? What factors led to the DNF? Ask yourself these questions, including what needs to be accounted for and what to improve on for next time.

Like any “failure” in life, a DNF is a springboard for growth, improvement, and eventual success.

What Is A DNS In Running?

Last but not least, what is a DNS in running?

DNS is another common initialism used among runners that means “did not start”.

DNS is worth mentioning here as it is something that should be considered in the same regard as a DNF.

In fact, some of the above reasons for DNFing a run apply just as much as to DNSing, such as pain, injury, lack of focus, and danger. 

If, for any of the above reasons, you feel that it is not worth starting a race right from the outset, the same notion applies: a running DNS is perfectly acceptable and there should be nothing to stop you if you feel that it is the right decision.


A DNF in running is an initialism that stands for “did not finish”. It is typically used in long-distance running events, describing when a runner is not able to reach the finish line due to one or several factors. 

These factors include pain and injury, runner’s wall, danger, poor mental state, shoe degradation, and missing the cut-off time.

Knowing when to DNF a run is important and perfectly acceptable no matter the personal reasons behind the decision.

Ultimately, a running DNF is a necessary learning experience for all runners that can shed light on what went wrong, individual factors that need to be worked on, and how to improve, as well as perform to your best ability, next time.

Megan Rinzel
Latest posts by Megan Rinzel (see all)