Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.
What Is a Subungual Hematoma?
A subungual hematoma is a collection of blood beneath the toenail (or fingernail) that results from injury to the blood vessels under the nail plate. The trapped blood has no escape route, producing pressure that causes intense, throbbing pain—often disproportionately severe relative to the apparent injury. Subungual hematomas are most commonly caused by acute trauma (dropping a heavy object on the toe, stubbing the toe against furniture or a door) or by repetitive microtrauma in runners and hikers (the “black toenail” that develops from chronic nail-to-shoe impact).
Causes of Blood Under the Toenail
Acute Trauma
Crushing injuries—dropping heavy objects on the foot, severe stubbing, or door slams—produce immediate, dramatic subungual hematoma with intense pain and visible dark discoloration under the nail within minutes to hours. The nail plate itself may be intact or cracked. When the nail is cracked and the hematoma is communicating with a wound, the risk of infection increases and evaluation is warranted. Large hematomas covering more than 50% of the nail surface are associated with higher rates of underlying nail bed laceration, which may affect nail regrowth.
Runner’s Toenail (Repetitive Microtrauma)
Runner’s black toenail—chronic subungual hematoma from repetitive nail impact against the shoe toe box during running or hiking—is one of the most common foot problems in endurance athletes. The second toenail (which is often the longest) or great toenail are most frequently affected. The mechanism is the nail repeatedly striking the shoe interior on downhill running, long distances, or in shoes that are too small or have insufficient toe box depth. Unlike acute hematomas, runner’s black toenail develops gradually over weeks, is usually painless or mildly sore, and the nail eventually separates and is replaced by a new nail over 3–6 months.
Treatment: When to Drain and When to Watch
The primary indication for draining a subungual hematoma is severe pain that requires relief—not appearance. Nail trephination (creating a small hole through the nail plate to allow blood drainage) is a simple, highly effective procedure that immediately reduces pressure and pain. It is performed with a heated wire or cautery device (making a small hole through the nail) or a fine-bore needle under sterile conditions. Trephination is indicated when the hematoma is painful, large (covering more than 25–50% of the nail), and acute (within 24–48 hours—blood must be liquid to drain). After 48–72 hours, blood begins to coagulate and may not drain effectively.
Small, minimally painful hematomas require no treatment beyond protection—the blood will be slowly reabsorbed or will grow out with the nail over weeks to months. The nail may loosen (onycholysis) and eventually separate as the new nail grows underneath. Protecting the nail with a foam toe cap during this process prevents pain from pressure or catching. Avoid cutting or prying the nail off—it provides a protective layer for the nail bed as the new nail grows underneath.
Do You Need an X-ray?
Significant trauma to the toe sufficient to cause a large subungual hematoma often also fractures the underlying distal phalanx (the tip of the toe bone). The nail-bone relationship means that any large traumatic hematoma warrants X-ray evaluation to identify an underlying fracture—particularly if there is deformity, significant pain with movement of the toe, or if the injury involved crushing force. An open nail bed laceration with a distal phalanx fracture is classified as an open fracture, requiring more aggressive wound care and potentially antibiotics. The nail itself can be considered a “soft cast” that provides alignment for the underlying bone; preserving it (when intact and not severely disrupted) allows better healing of the nail bed.
Subungual Hematoma vs. Nail Melanoma
The most important diagnostic distinction is distinguishing a subungual hematoma from subungual melanoma (nail cancer). A traumatic hematoma is typically: red-to-dark-purple (not true black-brown), associated with a clear trauma event, irregular in shape (like a bruise), and grows out with the nail over weeks to months—the discoloration moves toward the nail tip as the nail grows. A melanoma streak is true dark-brown or black, a vertical band from the nail base to the tip, persistent or growing wider over time, and may show Hutchinson’s sign (pigment extending onto the nail fold skin). Any dark nail discoloration without a clear traumatic cause, discoloration that doesn’t grow out with the nail after 4–6 months, or pigmentation with atypical features should be evaluated by a podiatrist or dermatologist.
Frequently Asked Questions
How long does a subungual hematoma take to go away?
The pain from a traumatic subungual hematoma typically subsides significantly within 24–72 hours—faster if the hematoma was drained. The visible discoloration grows out with the nail over 3–6 months as the new nail replaces the stained portion. If the nail loosens and falls off (which commonly happens after large hematomas), the underlying new nail is already growing and will fully replace the lost nail in 6–12 months. Runner’s black toenails from chronic microtrauma may recur with each training cycle until shoe fit is corrected—the key is ensuring adequate toe box length (1–1.5 cm of space from the longest toe to the end of the shoe) and width.
Should I drain blood under my toenail at home?
Home drainage attempts carry significant risks—needle puncture through the nail without sterile technique can introduce infection into the nail bed, and improper technique can damage the nail bed or cause the nail to avulse (pull away). If pain is severe and you are not able to see a podiatrist within 24 hours, some emergency medicine providers perform nail trephination—but this is generally safer done in a clinical setting than at home. For most patients, the discomfort from an untreated hematoma reduces naturally within 48–72 hours as the blood pressure equalizes. If pain is manageable, elevation and over-the-counter pain medication (ibuprofen) are appropriate while awaiting professional evaluation.
How do I prevent runner’s black toenail?
The primary prevention is properly fitted running shoes with adequate length and width. Running shoes should have 1–1.5 cm (about a thumb’s width) of space between the longest toe and the end of the shoe—because feet swell with exercise and the foot slides forward on downhills. Lace-locking techniques (creating a heel lock with the top two eyelets) prevent the foot from sliding forward in the shoe on downhill sections. Keeping toenails trimmed short (but not too short) reduces the nail surface that contacts the shoe. Moisture-wicking socks that prevent slippage and reduce shear forces help. Athletes with persistently recurrent black toenail despite shoe correction may have an unusually long second toe or nail bed anatomy that makes them prone—a podiatrist can assess whether nail reduction or matrix narrowing would help.
Medical References & Sources
- PubMed Research — Subungual Hematoma Treatment
- PubMed Research — Runner’s Toenail Microtrauma
- American Academy of Dermatology — Distinguishing Nail Hematoma from Melanoma
Dr. Tom Biernacki, DPM is a board-certified podiatric surgeon at Balance Foot & Ankle in Howell and Bloomfield Hills, Michigan. He evaluates and treats subungual hematomas, nail bed injuries, and concerning nail pigmentation including nail melanoma evaluation and biopsy.
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Subscribe on YouTube →Medically Reviewed by: Dr. Tom Biernacki, DPM — Board-Certified Podiatrist, Balance Foot & Ankle Specialists
Blood Under Your Toenail?
A subungual hematoma can be very painful and may need professional drainage. Our podiatrists provide quick, safe relief — often in a single visit.
Sources
- Roser SE, Gellman H. “Comparison of nail bed repair versus nail trephination for subungual hematomas in children.” J Hand Surg Am. 1999;24(6):1166-1170.
- Meek S, White M. “Subungual haematomas: is simple trephining enough?” J Accid Emerg Med. 1998;15(4):272-273.
- Wang QC, Johnson BA. “Fingertip injuries.” Am Fam Physician. 2001;63(10):1961-1966.
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.
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