If You’re Losing Toenails From Running, Read This

It usually starts subtly.

A little pressure at the end of a long run. A nail that feels tender in your shoe. Maybe some dark discoloration you assume will grow out.

Then suddenly, the nail lifts. Or falls off.

For many runners, black toenails feel like a badge of honor. A sign of mileage. Proof of effort. But losing toenails from running is not something you should simply accept.

At ARCH by Dr. Krista Archer on the Upper East Side of Manhattan, nail trauma is one of the most common issues we see during peak training cycles. And while it’s common, it’s rarely random.

What Actually Causes Black Toenails in Runners

Black toenails are usually caused by repeated micro-trauma inside the shoe. With every stride, your foot moves slightly forward. If there’s friction, pressure, or impact at the front of the shoe, the nail absorbs that force over thousands of steps.

Underneath the nail plate is a sensitive nail bed rich in small blood vessels. When those vessels break from repetitive pressure, blood pools beneath the nail, creating the dark discoloration runners notice. This is called a subungual hematoma.

Sometimes it’s painful. Sometimes it isn’t.

But discoloration is a signal that the nail has been stressed beyond tolerance.

It’s Not Just About Shoe Size

Most runners assume the problem is that their shoes are too small.

Sometimes that’s true. But more often, the issue is more nuanced. Toe box shape, lacing technique, downhill running, swelling during longer mileage, and even subtle gait mechanics can all contribute to nail trauma.

Your foot naturally swells during exercise. If your shoes don’t accommodate that expansion, pressure increases at the front of the shoe. Over time, that repeated compression can cause the nail to loosen or detach entirely.

Biomechanics matter here too. If your stride causes excessive forward slide within the shoe, the nail becomes the impact point.

Why Losing a Toenail Isn’t “No Big Deal”

Many runners ignore black toenails until the nail falls off. While some cases resolve without complication, nail loss creates vulnerability.

Without the nail plate, the nail bed is exposed. That increases the risk of infection, fungal colonization, and abnormal regrowth. In some cases, repeated trauma can permanently alter how the nail grows back, leading to thickening or chronic discoloration.

Healthy nails protect the toe. They’re not decorative — they’re structural.

Prevention Is More Technical Than You Think

Preventing toenail trauma starts with proper shoe selection. That includes adequate length, appropriate toe box width, and ensuring enough vertical depth to prevent nail compression. Runners often focus on cushioning and stability but overlook forefoot space.

Lacing techniques can also reduce forward slide. Small adjustments can significantly change pressure distribution.

Maintaining proper nail length matters as well. Nails that are too long are more likely to hit the front of the shoe. Nails that are aggressively cut too short can create ingrown edges and additional complications.

For runners logging high mileage in New York City — where pavement is unforgiving and step counts are elevated even outside of training — precision matters.

When to See a Podiatrist

If a black toenail is extremely painful, rapidly swelling, draining, or accompanied by redness around the nail fold, evaluation is important. In some cases, pressure beneath the nail needs to be relieved.

If the nail falls off completely, protecting the exposed nail bed properly reduces the risk of infection and supports healthier regrowth.

Dr. Krista Archer, Board Certified Podiatrist, evaluates runners at her Upper East Side Manhattan office to determine whether nail trauma is purely mechanical or if additional intervention is needed.

Early care often prevents long-term nail distortion.

Nail Recovery and Aesthetic Concerns

For many runners, appearance matters too — especially in warmer months.

When a nail regrows abnormally or thickens after repeated trauma, restoration options may be appropriate. Maintaining healthy surrounding skin and cuticle structure supports stronger regrowth. Medical-grade foot care and targeted skin support through ARCH by Dr. Krista Archer can also help maintain the integrity of the nail environment during recovery.

Function and aesthetics are not separate conversations. Healthy tissue supports healthy appearance.

The Smarter Approach for Runners

Black toenails are common in runners, but they are not inevitable.

They are often a sign that something about your footwear, mechanics, or training load needs adjustment.

Instead of accepting nail loss as part of the sport, consider it feedback.

If you’re repeatedly losing toenails, noticing persistent discoloration, or concerned about regrowth, schedule an evaluation at our Upper East Side office. Identifying the mechanical cause early can protect both performance and long-term nail health.

Your training should build strength — not compromise it.