Black Toenail: Causes, When to Worry, and Treatment

Quick answer: Treatment for black toenail causes treatment follows a stepwise approach: 1) conservative care first (rest, ice, supportive footwear, OTC anti-inflammatories), 2) physical therapy and targeted exercises, 3) in-office treatments (injections, custom orthotics) if conservative fails at 4-6 weeks, 4) surgery for refractory cases. Most patients resolve at step 1 or 2. Call (810) 206-1402.

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

A black or dark toenail can range from a completely benign bruise under the nail from running to a serious condition requiring urgent medical evaluation. Understanding the possible causes helps you determine whether watchful waiting or a prompt podiatry visit is appropriate.

Most Common Cause: Subungual Hematoma

The most common cause of a black toenail is a subungual hematoma — bleeding under the nail plate from direct trauma. This occurs from:

• Running and hiking — repetitive microtrauma from the toe hitting the front of the shoe during downhill running or long-distance running; extremely common in marathon runners and hikers (“runner’s toenail”)
• Acute trauma — dropping a heavy object on the foot, stubbing the toe, or a sports injury
• Ill-fitting footwear — shoes that are too short, too narrow, or have a low toe box compress the nail continuously

A traumatic subungual hematoma typically presents as a dark red, purple, or black discoloration under the nail that appears shortly after injury, accompanied by nail tenderness. Small hematomas (occupying less than 25–50% of the nail) typically resolve on their own as the nail grows out. Larger, painful hematomas can be drained (trephination) for immediate pain relief.

Toenail Fungus (Advanced)

Advanced toenail fungus (onychomycosis) can produce dark brown or black discoloration due to debris and pigment-producing fungal species. Fungal black toenails are typically distinguished by the gradual onset, thickened and brittle nail texture, and absence of trauma history. Fungal culture or nail clipping analysis confirms the diagnosis.

Subungual Melanoma: The Critical Diagnosis Not to Miss

Subungual melanoma — melanoma originating beneath the toenail — is a potentially life-threatening condition that can present as a dark streak or diffuse nail discoloration. The “ABCDEF” rule helps identify concerning features:

• Age 20–90, African American, Asian, or Native American ethnicity (higher incidence)
• Band width greater than 3mm or irregular borders
• Change in the lesion or lack of Change despite nail growth
• Digit involved — thumb, index finger, or hallux (big toe) are most common
• Extension of pigment onto the skin fold adjacent to the nail (Hutchinson’s sign)
• Family history of melanoma or personal melanoma history

Any unexplained nail discoloration without a clear trauma history warrants prompt podiatric or dermatologic evaluation. Subungual melanoma is most curable when identified early. Biopsy is the definitive diagnostic test.

Other Causes of Black Toenail

• Topical product staining — some dark nail polishes or certain medications can discolor nails
• Peripheral vascular disease — severe circulatory compromise can cause nail changes and discoloration
• Peutz-Jeghers syndrome — a rare genetic condition producing nail pigmentation

When to See a Podiatrist

Seek evaluation for a black toenail when: there is no clear traumatic cause, the discoloration is not growing out with the nail, there is a brown-black streak (rather than a diffuse hematoma), the pigment extends onto the skin around the nail, the nail is painful without a trauma history, or you have a personal or family history of melanoma.

Visit Balance Foot & Ankle — Same-Day Appointments Available

Our podiatry team serves patients throughout Michigan including Howell, Brighton, and Bloomfield Hills. If you’re dealing with heel pain, ingrown toenails, or a foot injury, we have same-day appointment availability.

Frequently Asked Questions

How long does treatment take to work?

Most patients see improvement in 4-8 weeks with consistent conservative care. Persistent symptoms after 8 weeks need imaging and escalation.

When is surgery needed?

Surgery is reserved for cases that fail 3-6 months of conservative care, structural deformities, or fractures requiring stabilization.

Is this covered by insurance?

Most diagnostic visits and conservative treatments are covered by Medicare and major insurers. Custom orthotics often require diabetic or post-surgical justification.

What is Foot pain?

Foot pain is a common foot/ankle condition that affects mobility and quality of life. Understanding the underlying cause is the first step in successful treatment. Our podiatrists at Balance Foot & Ankle perform a hands-on biomechanical exam, review your activity history, and use diagnostic imaging when appropriate to identify the root cause—not just treat the symptom. Many patients have been told to “rest and ice” without a deeper diagnostic workup; our approach is different.

Symptoms and warning signs

Common signs of foot pain include pain that worsens with activity, morning stiffness, swelling, tenderness when palpated, and difficulty bearing weight. If you experience sudden severe pain, inability to walk, visible deformity, numbness or color change, contact our office the same day or visit urgent care—these can signal a more serious injury such as a fracture, tendon rupture, or vascular compromise. Diabetics with any foot wound should seek same-day care.

Conservative treatment options

Most cases of foot pain respond to non-surgical care: structured rest, supportive footwear changes, custom orthotics, targeted stretching and strengthening protocols, anti-inflammatory medications when medically appropriate, and in-office procedures such as ultrasound-guided injections. We also offer advanced therapies including MLS laser therapy, EPAT/shockwave, regenerative injections, and image-guided procedures. Treatment is sequenced from least invasive to most invasive, and we explain the rationale at every step.

When is surgery considered?

Surgery is reserved for cases that fail 3-6 months of well-structured conservative care, when there is structural pathology (severe deformity, complete tear, advanced arthritis), or when imaging shows damage that will not heal without intervention. Our surgeons have performed 3,000+ foot and ankle procedures and prioritize minimally-invasive techniques whenever appropriate. We discuss recovery timelines, return-to-activity milestones, and realistic outcome expectations before any procedure is scheduled.

Recovery timeline and prevention

Recovery from foot pain varies based on severity and chosen treatment path. Conservative cases often improve within 4-8 weeks with consistent adherence to the protocol. Post-procedural recovery may range from a few days (in-office procedures) to several months (reconstructive surgery). Long-term prevention involves footwear assessment, activity modification, structured strengthening, and regular check-ins with your podiatrist if you have a history of recurrence. We provide written home-exercise plans and digital follow-up support.

Related Care at Balance Foot & Ankle

Clinical toenail services at our Howell and Bloomfield Hills offices.

Ingrown Toenail TreatmentToenail MatrixectomyMedical Pedicure