Medically reviewed by Dr. Tom Biernacki, DPM · Board-Certified Podiatric Surgeon · Last reviewed: April 2026 · Editorial Policy
Quick Answer
Black Toenail: Causes, When to Worry, and Treatment relates to toenail conditions — typically caused by fungal infection or trauma. Most patients improve in 6-12 months for nail regrowth with conservative care. Same-week appointments in Howell + Bloomfield Twp: (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.
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Medically Reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatrist, Balance Foot & Ankle Specialists, Michigan. 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.
Unexplained Nail Change? Don’t Wait.
Dr. Biernacki at Balance Foot & Ankle evaluates nail changes including trauma, fungal infection, and pigmented lesions. Same-week appointments available in Howell and Bloomfield Hills.
or call (810) 206-1402
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When to See a Podiatrist
If foot or ankle pain has been bothering you for more than a few weeks, home care alone may not be enough. Balance Foot & Ankle offers same-week appointments at our Howell and Bloomfield Hills clinics — no referral needed in most cases. Bring your current shoes and a short list of symptoms and we’ll build you a treatment plan in one visit.
Call Balance Foot & Ankle: (810) 206-1402 · Book online · Offices in Howell & Bloomfield Hills
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Podiatrist-recommended products
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Reduce nail trauma that causes subungual hematomas.
View on Amazon →Reduce forward slide in running shoes that bruises nails.
View on Amazon →Ice the toe after nail trauma to reduce pressure.
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View on Amazon →Related resources
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Advantages
- ✓ Most cases resolve at home
- ✓ Same-week appointments available
- ✓ Permanent fix exists
Considerations
- ✗ Recurrence common without prevention
- ✗ Diabetics need professional care
Dr. Tom’s Recommended Products for toenail conditions
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About Your Care Team at Balance Foot & Ankle
Dr. Tom Biernacki, DPM · Board-Certified Foot & Ankle Surgeon. Specializes in conservative-first care, minimally invasive bunion surgery, and complex reconstruction.
Dr. Carl Jay, DPM · Accepting new patients. Specializes in sports medicine, athletic injuries, and routine podiatric care.
Dr. Daria Gutkin, DPM, AACFAS · Accepting new patients. Specializes in surgical reconstruction and pediatric podiatry.
Locations: 4330 E Grand River Ave, Howell, MI 48843 · 43494 Woodward Ave Suite 208, Bloomfield Twp, MI 48302
Hours: Mon–Fri 8:00 AM – 5:00 PM · (810) 206-1402
Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.
- Diagnosis and Treatment of Plantar Fasciitis (PubMed / AAFP)
- Heel Pain (APMA)
- Hallux Valgus (Bunions): Evaluation and Management (PubMed)
- Bunions (Mayo Clinic)
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