Black Toenail

Toenails can become black due to nutritional shortfalls, infections, or physical injury. In many cases this will resolve by itself. If it persists, consult your physician to exclude a more serious origin.

Below we explore the reasons behind black toenails and the treatment choices.

What leads to black toenails?

A toenail may darken for several reasons, including:

• An underlying medical condition: Conditions such as anemia, diabetes, cardiovascular disease, or kidney disease can produce discoloration.
• Fungal infections: Although fungal nails commonly appear white or yellow, a build-up of debris from an infection can sometimes make nails look black. Toenails are particularly susceptible because fungi thrive in warm, moist settings.
• Melanoma: The most serious form of skin cancer often shows as an irregular dark brown patch. Similar dark spots can develop beneath the nail plate.
• Trauma: Injury to the nail can break blood vessels underneath, causing bleeding beneath the nail that appears black.

When should you see a doctor?

A black toenail doesn’t always require medical attention — whether you need to see a doctor depends on the cause. Identifying the reason can guide your choice. If the cause is unknown, it’s wise to consult a doctor to rule out a serious condition.

Not every case of toenail fungus needs a medical visit, but if you have diabetes you should seek professional care.

A dermatologist can diagnose and manage black toenails. If you suspect melanoma, a dermatologist’s evaluation is necessary. When the discoloration stems from another health issue, such as diabetes, coordination with your primary care provider is also important to address the root problem.

Any blackened toenail that doesn’t resolve should be evaluated by a physician. If you’re worried and don’t have a dermatologist, you can find local specialists through the Healthline FindCare tool .

Can black toenails lead to complications?

Untreated toenail fungus can spread across the feet and to other body areas, and may permanently damage the nail.

Misdiagnosing melanoma as a trauma-related black nail can delay needed treatment. It’s important to see a doctor if you notice black spots that seem to expand across the nail or that don’t disappear as the nail grows out.

What treatments are available for black toenails?

Toenail fungal infections are often manageable at home if caught early. OTC ointments, creams, and nail polishes are commonly effective. More severe infections may need prescription antifungal medications.

If the blackening is from trauma, the dark area caused by bleeding under the nail will fade as the nail grows out.

Trauma-induced black toenails typically resolve without intervention. If the nail still looks black after it has grown out, another underlying cause may be responsible.

Discoloration linked to diabetes or other systemic conditions requires treating the underlying disease.

Q&A: Black toenail from running

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What is the prognosis for a black toenail?

The outlook depends mainly on the underlying cause. Trauma-related and fungal cases generally have the best prognosis: injured nails grow out and many fungal infections can be treated successfully at home.

Black nails due to melanoma or systemic disease reflect an underlying illness. The prognosis for those situations depends on how promptly the underlying condition is diagnosed and treated.

How can you prevent black toenails?

Keeping nails clean and dry can help prevent some causes of darkened toenails. Protecting your toes from injury—by wearing closed-toe shoes when handling heavy objects and selecting properly fitting footwear for exercise, especially running—can reduce trauma risk.

For other causes, take targeted preventive steps. Limiting direct sun exposure to your feet and applying sunscreen on your toes can lower melanoma risk. Discoloration from other medical conditions can be reduced by effective treatment and management of the underlying illness.