Maybe it started as a sore toe after a long run, a stubbed foot, or shoes that felt a little too tight. Then one day, you looked down… and your toenail had turned black!
Don’t panic. A black toenail is usually the result of a minor injury, repetitive pressure, or a harmless condition. But sometimes, it’s your body’s way of signaling a bigger issue. Here’s what causes toenails to turn black, what to expect next, what to do right away, and when it’s time to make an appointment.
What causes a black toenail?
A black toenail is most often caused by bruising or bleeding under the toenail, known as a subungual hematoma. This can happen when the toenail experiences sudden trauma, such as stubbing your toe or dropping something heavy on it. It can also be the result of repetitive stress from running, hiking, or playing sports, especially when combined with tight or poorly fitting footwear.
In some cases, a black toenail may be caused by a fungal infection, which can darken the nail over time. Less commonly, it could be related to underlying health issues like diabetes, poor circulation, or (very rarely) a form of skin cancer under the nail.
Who gets black toenails the most?
Anyone can develop a black toenail, but some people are more prone to it than others. If you’re a runner, hiker, or athlete, repeated impact and pressure on your toes can cause bruising beneath the nail. Kids often experience toenail injuries simply from rough-and-tumble play or shoes that don’t quite fit right. Older adults may also be at higher risk due to thinner nails, decreased circulation, or underlying health conditions. People with diabetes should pay especially close attention—changes in the toenail color or shape can be a sign of something more serious.
You may be more likely to develop a black toenail if you’re physically active, have circulation issues, wear tight shoes often, or have medical conditions that affect the feet.
What happens when your toenail turns black?
Depending on the cause, a black toenail might appear gradually or show up all at once. You may feel pain or pressure under the nail, especially if the discoloration is from trapped blood. The nail might loosen or lift away from the nail bed, and in some cases, it may fall off entirely. In other situations, the nail simply appears darker without causing discomfort. Often, the dark area will grow out with the nail over time, but it’s important to monitor for signs of infection or other complications. When it doubt, our doctors are ready to answer your questions!
What to do if you think your toenail has turned black
If your toenail has recently turned black or is heading in that direction, start by resting your foot and elevating it if you suspect injury. Soaking the toe in cool water may help reduce swelling and pressure. Avoid tight shoes, especially those that rub or press against the nail. Keep an eye on the nail and consider taking a photo so you can monitor how it changes over the next few days. If the discoloration is widespread, painful, or worsening, it’s best to contact a podiatrist for evaluation.
When to call us
It’s time to call Beyond Podiatry if the nail is painful to the touch, appears infected, or has started lifting or separating from the nail bed. People with diabetes or poor circulation should never ignore a black toenail, even if it seems minor. One of our doctors can determine whether the nail needs to be drained, monitored, or biopsied. If the black area is growing, changing shape, or wasn’t caused by a clear injury, prompt medical attention is even more important.
When to go directly to the emergency room
Some black toenails are a sign of more serious injury. Go to the ER if think your toe might be broken, if you have severe pain or swelling after impact, or if the area shows signs of a spreading infection such as fever, red streaks, or heat coming from the toe.
The Bottom Line on Black Toenails
A black toenail can be caused by something as simple as bumping your toe – or it might be your body’s way of flagging something more serious. Whether it’s from a toenail injury, a fungal infection, or an underlying condition, it’s always smart to pay attention. Still unsure? Don’t guess. Make an appointment with one of our podiatrists to get a clear diagnosis and peace of mind.
