Discovering a dark patch beneath your toenail can understandably cause concern. In most cases we see in clinic, it is a subungual haematoma, a bruise caused by bleeding under the nail after a stubbed toe or repetitive pressure from running. Less often, the discolouration is due to a fungal nail infection, which tends to develop gradually over months, and only rarely does it indicate a more serious condition such as subungual melanoma.
A few key clinical features help us tell these conditions apart. One of the most useful is where the dark mark first appeared and how it changes over time. A bruise usually follows a clear injury and gradually grows out with the nail, whereas a dark streak that begins at the base of the nail without any known trauma warrants prompt assessment by a podiatrist or GP.
In This Article
- Most black toenails are subungual haematomas from a knock, long run, or ill-fitting shoes, often throbbing at first, then settling over days.
- A bruise moves toward the tip as the nail grows, with clear nail appearing at the cuticle within weeks.
- Fungal infection usually develops over months, causing yellow-brown, thickened, crumbly nails with dark debris that can mimic bruising.
- Melanoma is rare, but seek review for a dark streak from the cuticle that widens, darkens, spreads onto skin, or doesn’t grow out.
- Most bruises need little treatment; avoid home drainage, and see a podiatrist promptly if diabetic, on blood thinners, or without clear injury.
Why Has My Toenail Turned Black?
If you’ve just spotted a dark toenail after a long run on the Main Yarra Trail or a stubbed toe at home, it’s natural to worry, but in many cases the cause is far less serious than you might fear. It’s most often blood trapped under the nail from a knock or from your toe repeatedly hitting the front of your shoe, though a fungal nail infection, certain medicines, some health conditions and a few less common causes can also darken a nail.
Knowing which one fits your situation can help you decide whether to watch it grow out or see your GP or podiatrist sooner.
Bleeding Under the Nail From a Knock or a Long Run
When a toenail turns black after a long run, a new pair of shoes or a stubbed toe, the most common cause is blood trapped beneath the nail plate. Clinically, we call this a subungual haematoma, which simply means a bruise under the nail.
It can follow a single knock, such as dropping something on your foot, but in runners it more often develops gradually as the toe repeatedly strikes the front of the shoe, particularly on downhill stretches or in footwear that’s slightly too short.
This is why it’s commonly known as runner’s toe, and many patients don’t recall any specific injury at all. A black toenail from running may feel painful and throbbing at first before settling over the following days.
If it’s fresh and throbbing, please don’t pierce it yourself; book online or call Bellevue Podiatry on (03) 9457 2336 so we can assess it and, where appropriate, safely relieve the pressure.
Fungal Nail Infection
While most black toenails are caused by bruising, a fungal nail infection (onychomycosis) can also change the nail’s colour. It usually appears yellow-brown, but debris under the nail can look darker, which is why black toenail fungus is sometimes mistaken for a bruise.
| Feature | Bruise | Fungal Nail |
|---|---|---|
| Onset | Often sudden, after a knock or a run | Gradual, over months |
| Nail texture | Usually smooth | Often thickened and crumbly |
If you’re wondering how to get rid of black toenails caused by fungus, patience is essential, as treatment often takes months while healthy nail grows. A podiatrist can assess the nail, reduce nail thickness and discuss evidence-based treatment options suited to your situation.
This is general information and not a substitute for an individual assessment. Book online or call Bellevue Podiatry on (03) 9457 2336.
Medicines, Health Conditions and Other Less Common Causes
Not every black toenail is caused by trauma or a fungal infection. In clinic, we also consider medications, underlying health conditions and, rarely, changes that need closer medical review.
Medications
If you take blood thinners (anticoagulants), even a minor knock can cause more bleeding beneath the nail, forming a subungual haematoma. Certain other medicines can also cause nail discolouration over time.
Black Toenail and Diabetes
The main black toenail diabetes concern is that peripheral neuropathy (reduced sensation) or poor circulation can stop you from feeling an injury, so it may go unnoticed and heal more slowly.
If you have diabetes and notice nail darkening, see a podiatrist promptly rather than waiting.
Black Toenail Melanoma
Black toenail melanoma (subungual melanoma) is rare. However, please see your GP if there’s no clear cause for the discolouration, or if you notice:
& A dark streak beginning at the cuticle
& A streak that widens or darkens over time
& Pigment spreading onto the surrounding skin
& Discolouration that doesn’t grow forward with the nail
Will My Black Toenail Fall Off?
Sometimes the nail lifts away from the nail bed and loosens. Often, though, the discoloured section simply grows out with the nail over several months.
To have your nail assessed, book online or call Bellevue Podiatry on (03) 9457 2336.
Bruise or Melanoma? How to Tell the Difference
For most patients, the clearest clue is time. A bruise moves forward as the nail grows, while a mark that needs checking tends to stay in place or grow.
Signs of a Toenail Bruise
A bruise under the nail, known as a subungual haematoma, usually follows a knock, a long downhill run or shoes that are too short.
It’s typically reddish-purple to black and may throb in the first day or two. As the nail plate grows, it carries the discolouration forward towards the tip of the toe.
Within a few weeks, you should see clear, healthy nail emerging at the cuticle.
Signs That May Point to Subungual Melanoma
Subungual melanoma is a rare form of skin cancer that develops beneath the nail, and it tends to behave differently from a bruise. Please see your GP promptly if there’s no likely cause for the mark, or if you notice a dark streak that:
& starts at the cuticle
& widens over time
& darkens in colour
& spreads onto the surrounding skin
& doesn’t move forward as the nail grows
If you’re unsure what you’re looking at, book online or call Bellevue Podiatry on (03) 9457 2336, and we can assess the nail for you.
What to Do About a Black Toenail, and How Long It Takes to Grow Out
Treating a Black Toenail
In most cases, a black toenail caused by a bruise, known clinically as a subungual haematoma, doesn’t need much treatment.
Most black toenails from a bruise, or subungual haematoma, need very little treatment and simply grow out on their own.
Once the initial tenderness settles, it’s usually left to grow out naturally. If the injury is fresh (within 48 hours) and throbbing, a clinician may drain the trapped blood to relieve pressure beneath the nail.
Please never attempt this at home, as it carries a real risk of infection and further damage to the nail bed.
How Long Does a Black Toenail Take to Grow Out?
Toenails grow about 1.6 mm a month, so clear, healthy nail often appears at the cuticle within a few weeks. The darkened section then moves gradually towards the tip as the nail grows.
A bruised nail on your big toe may take several months, and sometimes over a year, to clear completely.
This slower timeframe is normal and doesn’t usually indicate a problem with healing.
When to See a Podiatrist
Please see a podiatrist promptly if any of the following apply:
& You have diabetes
& You have poor circulation
& You have numb feet or reduced sensation
& You take blood thinners
& The discolouration appeared without any injury you can recall
To identify the cause of a black toenail, such as poor shoe fit, book online or call Bellevue Podiatry on (03) 9457 2336.
How to Lower the Chance of Another Black Toenail
Most black toenails, known clinically as a subungual haematoma, develop when the toe repeatedly strikes the front of the shoe. Small adjustments to your footwear and running habits can often reduce the risk of it recurring.
In clinic, we generally recommend these practical steps:
- Check shoe fit late in the day: Feet swell slightly as the day goes on, so this gives a more accurate sense of fit.
- Allow adequate toe box room: Aim for about a thumb’s width of space beyond your longest toe.
- Use heel lock lacing: Threading through the extra top eyelet helps stop your foot sliding forward on steep downhill stretches, such as those on the Main Yarra or Plenty River trails.
- Maintain nail care: Keep your toenails trimmed straight across and not too long.
If you have had repeated black toenails, a podiatrist can assess your shoe fit, lacing and gait to identify the underlying cause.
Frequently Asked Questions
Can I Keep Running While I Have a Black Toenail?
In many cases, yes, you can continue running if the affected toe isn’t particularly painful.
A black toenail, known clinically as a subungual haematoma, is a collection of blood beneath the nail plate that’s usually caused by the toe repeatedly striking the front of the shoe.
Reducing Pressure on the Nail
Simple footwear adjustments can protect the injured nail and help prevent the problem from recurring.
- Check your shoe length: Make sure your shoes aren’t too short. Allow roughly a thumb’s width between your longest toe and the end of the shoe.
- Adjust your lacing: Use a heel-lock lacing technique so your foot doesn’t slide forward, particularly on downhill sections.
- Trim your nails: Keep your toenails trimmed straight across and not too long to reduce contact with the toe box.
When to Ease Off
If the toe is throbbing or the pressure under the nail is painful, reduce your running and see a clinician within about 48 hours. Within this window, drainage of the trapped blood is often possible and can relieve pressure quickly.
Seek prompt assessment if you notice increasing redness, swelling, warmth or discharge around the nail, as these may indicate infection.
Who Should Seek Care Promptly
If you have diabetes, reduced sensation in your feet or take blood thinners, please see a podiatrist promptly rather than waiting. These factors can increase the risk of complications and may allow a minor injury to go unnoticed.
Any dark discolouration that appears without a known injury, or that doesn’t grow out with the nail, should also be assessed.
Book an Appointment
Book online or call Bellevue Podiatry on (03) 9457 2336 to arrange an assessment with one of our podiatrists.
Will My Black Toenail Fall Off, and What Should I Do if It Does?
It may. When blood collects beneath the nail (a subungual haematoma), the pressure can separate the nail plate from the nail bed, and the nail may gradually lift as new nail grows behind it, although many bruised nails remain attached.
If your nail loosens, avoid pulling it off, as this can expose the sensitive nail bed and increase the risk of infection. Instead, follow these steps while the new nail grows through:
- Keep the toe clean and dry, washing it gently each day.
- Cover it with a light, breathable dressing.
- Wear roomy, well-fitted shoes to reduce pressure on the toe.
- Carefully trim any loose edges with clean clippers to prevent snagging.
If you have diabetes, reduced sensation in your feet, or signs of infection such as increasing redness, swelling, warmth or pus, book online or call Bellevue Podiatry on (03) 9457 2336.
This is general information and not a substitute for an individual assessment.
Is It Okay to Wear Nail Polish Over a Black Toenail?
Wearing nail polish over a black toenail is generally acceptable for a special occasion, but it conceals the nail plate and prevents you from monitoring how the discolouration changes.
With a typical subungual haematoma (a bruise beneath the nail), we expect the dark area to grow forward with the nail over several months, so being able to see it’s clinically useful.
Polish can also mask important warning signs, such as a dark streak that begins at the cuticle and widens over time, which requires prompt professional assessment.
Ideally, leave the nail bare and check it regularly until the discolouration has fully grown out.
Will My New Toenail Grow Back Normally After a Black Toenail?
In most cases, yes. When the damaged nail lifts or falls off, a new nail usually regrows from the nail matrix at the base of the toe, provided the matrix itself wasn’t significantly injured.
Regrowth is gradual, and a big toenail can take 12 to 18 months to be fully replaced. Some patients find the new nail grows back thicker, ridged or slightly misshapen, particularly after severe or repeated trauma.
If you’re concerned about how your nail is regrowing, or you have diabetes or poor circulation, book online or call Bellevue Podiatry on (03) 9457 2336. This is general information only and doesn’t replace an individual clinical assessment.
Do I Need a GP Referral to See a Podiatrist at Bellevue Podiatry?
No, you don’t need a GP referral to see a podiatrist at Bellevue Podiatry. You can book directly online or call our clinic on (03) 9457 2336.
If you live with a chronic condition such as diabetes, your GP may be able to arrange a care plan that makes some podiatry visits eligible for a Medicare rebate.
It’s worth raising this at your next GP appointment, particularly if you require ongoing foot care. Private health extras cover may also contribute towards your consultation.
We recommend checking your level of cover with your health fund before your visit so you know what to expect.
Conclusion
A black toenail can look alarming, but in most cases it’s simply a bruise that will gradually grow out towards the tip as your nail renews itself. Knowing what to watch for keeps you in control. Be alert to a dark streak that starts at the cuticle, widens, darkens or spreads onto the surrounding skin, and seek prompt care if you have severe pain, diabetes or take blood thinners. Otherwise, roomy footwear, neatly trimmed nails and a little patience will usually see your toe back to its best.
At Bellevue Podiatry, we help locals from Rosanna, Heidelberg, Watsonia, Ivanhoe and surrounding suburbs recognise the difference between a harmless knock, a fungal infection and something that warrants closer investigation. Our evidence-based approach is grounded in extensive clinical research, so you can feel confident that every assessment and treatment is designed to protect your long-term foot health.
