Should You Lose Toenails While Running?

The short answer: No.

Should You Lose Toenails While Running?

I’ve worked at a local running store for over 6 years now and one of the most common questions is: “should I lose toenails while running?”


One of the most important things I’ve learned is no matter the distance or amount you run, you should not have black toenails while running, and you should be losing toenails running. Blac toenails while running lead to loss of toenails. It’s a sign the shoe is too small or too narrow.

Black nails while running and toenail loss isn’t a sign of good training.  It’s not a runner’s “rite of passage.”  You are not a real runner once you have your first black nail or lose a toenail. In fact, losing toenails while running means the running shoe is ill fitting.

Finally, let’s not forget a toenail injury or runners toe is just gross. No one wants to go to the beach, missing half of their toenails.

Should You Lose Toenails While Running?How does a Lose of Toenails While Running Happen?

While running or working out, your feet tend to expand. It’s different for everyone, but most people’s feet swell a half size to full size (so yes, your feet are “bigger” after your done working out). It’s not just running long distance, but those who are on their feet all day like nurses or teachers.

When your feet expand, the top of your toenail starts jamming up against the front of the shoe. If your toenails continue to jam against the top of the shoe, they will bruise, turn black, and eventually fall off.  When you think about it, you are jamming your toenails against a shoe hundreds or even thousands of times per run. Your toes usually turn black and blue, and then your toenail falls off.

Most people lose their biggest toe or second toenail (depending on your longest toe).  If the shoe is not wide enough, you lose your pinkie toe. With injured toenails, you are more likely to get a fungal infection.

It doesn’t necessarily mean you need to go longer in a running shoe; you might just need to go wider or find a brand that fits your foot better.

Think about it this way: if you continue to punch your arm for an hour, it will bruise.  It’s the same with your feet.  It’s the same repetitive trauma.

Signs your running shoe fit is too small: 

  • Bruised, black toenails, and losing toenails running.
  • Damage to the nail bed or nail plate.
  • Toes going numb or tingling…(if your toes go numb the toe box is generally too narrow)
  • The lateral side of your shoe gets a hole in it (the shoe is too narrow)

How do you solve the problem of losing toenails while running? 

You should always go up a half size from your “normal” size. For instance, I wear a size 9.5 regular shoe. I wear a 10 or even 11 wide running shoe.  You shouldn’t say: “I’ve always worn X size shoe.” Like clothing brands, every brand creates its running shoes differently. In the running industry, your running shoe size might differ anywhere from 1-2 sizes or even a difference in width.

Things to Keep in Mind with the Correct Size of Running Shoes:

  • You should be able to wiggle all of your toes before, during, and after a run.
  • Your casual shoe and running shoe size are not usually the same size.
  • Your running shoe might “feel big,” but you want that extra space.
  • Having a shoe a half size bigger doesn’t cause issues. Having a running shoe a half size too small can cause running injuries like plantar fasciitis or neuromas.

In short, getting your foot correctly measured at a running store can make a huge difference. You don’t need to lose toenails while running, no matter if you are training for a 5k or 24-hour run.

Finally, have you subscribed to the LOLZletter? It’s a free newsletter that comes out each Monday. In the newsletter, I share running industry trends and things relevant to the sport. 

Question for you:

Have you ever had black toenails or lost toenails running? 

What running shoes do you currently wear?