Welcome
Most black toenails are a bruise. Here’s how to be more sure.
Finding a black toenail after a long run, a big walk or a stubbed toe is unsettling, and a quick search soon brings up the word melanoma.
The reassuring news is that most black toenails are simply blood trapped under the nail. But “most” isn’t “all”, and you deserve a better answer than “it’s probably nothing”.
This guide shows you a simple check that uses the way nails grow to tell a bruise from a mark that needs a closer look. It explains what to do in the meantime, and lists the signs that mean you should see your GP without waiting. It can’t diagnose you, but it can help you decide, calmly, what to do next.
Nicole Hardidge
Principal Podiatrist, Bellevue Podiatry
01 · The usual suspects
Why toenails turn black
In active adults, the most common cause is a bleed under the nail. Its medical name is a subungual haematoma, which simply means a collection of blood under the nail.
One knock, or a thousand small ones
Dropping something on your foot or stubbing your toe can cause a bleed straight away, and it usually throbs. More often in runners and walkers, the toe taps the front of the shoe again and again, especially on downhills or in shoes that are a little short. This is often called runner’s toe. It may not hurt much, and many people can’t remember a single moment when it happened.
Fungal nail infection
A fungal nail is usually thick, crumbly and yellow, white or brown, and only sometimes darker. Repeated rubbing from shoes can look very similar, so a lab test is recommended to confirm a fungal infection before tablet treatment starts.
Less common causes
Some medicines and some health conditions can change the colour of nails. Rarely, a dark mark is a melanoma under the nail. Unlike melanoma on sun-exposed skin, sun exposure doesn’t appear to be a risk factor for this type, so the useful thing to watch is how the mark behaves over time. That’s what the next section is for.
Pro tip from the clinic
If you remember when it happened, write the date down. A clear start date makes the grow-out check much easier to read.
02 · The grow-out check
The four-week grow-out check
Nails grow forward from the cuticle. A bruise sits under the nail and is carried forward with it, so within a few weeks a strip of clear, normal nail appears between the cuticle and the bruise. A streak that keeps running all the way back to the cuticle behaves differently, even if it seems to get longer.
Before you start
This check is for a mark you can link to a knock, tight shoes or a lot of running or walking. Even then, a knock doesn’t rule everything out, because small knocks are common and other causes can be blamed on them. If you have any of the signs in section 07, don’t wait four weeks. See your GP now.
- 1
Take a starting photo
In good daylight, photograph the toe from directly above, with a ruler or a coin beside it for scale. Note the date.
- 2
Check the back edge
Note whether the dark area touches the cuticle, the skin at the base of the nail, and if it doesn’t, how big the gap is.
- 3
Repeat once a week
Same light, same angle, same ruler, for four weeks.
- 4
Compare the first and last photos
Look for a band of clear nail opening up between the cuticle and the dark area. That gap is the sign you’re looking for.
Pro tip from the clinic
Toenails grow slowly, about 1.6 mm a month on average, so after four weeks you’re looking for a thin strip of new nail, not a big change. Leave nail polish off that toe until you’re done, or it will hide the very thing you’re watching.
03 · Your results
What your check is telling you
Match what you see to one of these three groups. If you’re not sure which fits, that’s normal, and it’s exactly what a check-up is for.
Clear nail at the cuticle
A gap is opening up
This is how a bruise behaves. It will keep growing out over the coming months and can be trimmed away as it reaches the tip.
Hard to tell
You can’t read the nail
A thick, ridged or slow-growing nail can be hard to read, even after four weeks. That’s common, and it isn’t a reason to keep waiting.
No clear nail, or a streak
A mark that needs a closer look
No clear nail at the cuticle after four weeks, a dark streak that runs right back to the cuticle, colour on the skin around the nail, or a mark that’s widening or changing are reasons to see your GP promptly.
04 · In the meantime
What to do right now
What helps depends on how fresh the bruise is and whether it hurts.
- 1
Fresh and throbbing (first 48 hours)
If a knock has left the toe very painful under pressure, a podiatrist or GP may be able to relieve it by releasing the blood through a tiny hole in the nail. This works most often within about 48 hours. Please don’t try it at home with a pin or a heated paperclip, which risks infection and burns.
- 2
Not painful, or more than a couple of days old
Usually the plan is to leave it alone and let it grow out. Rest from whatever caused it if the toe is sore, and wear roomier shoes for a while.
- 3
If the nail starts to lift
Don’t pull it off. Trim back only the loose part with clean clippers, keep the area clean and covered with a plaster, and watch for signs of infection.
- 4
If it looks infected or the toe may be broken
Spreading redness, heat, pus or pain that is getting worse, or a toe that is badly swollen or out of shape after a knock, needs a GP or podiatrist promptly.
Pro tip from the clinic
If you have diabetes, poor circulation or numb feet, skip the waiting game and have any nail change checked. Small foot injuries can be harder to notice and slower to heal.
05 · Common worries
Questions people often ask
Will my toenail fall off?
Sometimes. A large bleed can loosen the nail, which then lifts away over weeks as a new nail grows underneath. If it does come off, a toenail can take 12 to 18 months to grow back fully, and it may look a little different for a while.
How long until the black goes?
The mark grows out with the nail. At about 1.6 mm a month, a bruise halfway along a big toenail can take several months to reach the tip and be trimmed away.
Can I keep running?
If it isn’t sore, many people keep running. Fix the cause first, though: shoes that are a little short, loose lacing or long toenails will keep knocking the same spot. If it hurts, ease back until it settles.
Should I wear sunscreen on my toes?
It won’t hurt, but sun exposure doesn’t appear to be a risk factor for melanoma under the nail, so it isn’t a way to prevent it. Watching how the mark behaves is more useful.
Could it be fungus?
Possibly. Fungal nails are more often yellow, white or brown, and thick or crumbly. Because shoe damage can look similar, a lab test is recommended before starting tablet treatment.
Does a black toenail mean I have diabetes?
A black toenail on its own isn’t a sign of diabetes. But if you already have diabetes, have any nail change checked promptly rather than waiting.
06 · Prevention
Shoes, lacing and nails
If runs or long walks keep turning your nails black, the fix usually sits in your shoes.
Getting the fit right
- Leave room at the front. The Australian Podiatry Association suggests around 1.5 cm between your longest toe and the end of the shoe. Your big toe isn’t always the longest.
- Shop late in the day, when your feet are at their largest.
- Fit the bigger foot. Many people have one foot slightly bigger than the other.
- Keep toenails short and cut straight across, so the nail edge isn’t the first thing to hit the shoe.
Lace to stop the slide
If your foot slides forward in the shoe, your toes take the hit. Using the extra top eyelet to make a heel lock, sometimes called a runner’s loop, holds your heel back in the shoe and may help on downhills. Snug, not tight: you should still be able to wriggle your toes.
Long downhill runs and bigger training weeks before spring races are when toes take the most knocks. If you train on local trails like the Main Yarra or Plenty River trails, check your fit before you build your distance.
Pro tip from the clinic
Bring the shoes you were wearing when it happened to any appointment. The wear on the soles and the space at the toe tell us a lot.
07 · Warning signs
Signs to have it checked sooner
Most black toenails are harmless. These signs aren’t a reason to panic, but they are a reason to be seen rather than wait.
See your GP promptly if:
- You can’t link the mark to a knock, tight shoes or a lot of running or walking
- A brown or black streak runs all the way back to the cuticle
- The streak is about 3 mm wide or more, is getting wider or darker, or has uneven colour or blurry edges
- Colour has spread onto the skin around the nail (doctors call this Hutchinson’s sign)
- After four weeks of the grow-out check, there’s still no clear nail between the cuticle and the dark area
- The nail is splitting, lifting or bleeding without an injury
See a GP or podiatrist soon if:
- The toe is very painful, swollen or out of shape after a knock, or you can’t walk on it
- There are signs of infection: spreading redness, heat, pus or pain that is getting worse
- You have diabetes, poor circulation or numb feet
- You take blood-thinning medicine and the toe is badly bruised or painful
- Black toenails keep coming back
Your GP can examine the nail and, if a mark needs testing, refer you to a dermatologist. Bring your grow-out photos, as they show how the mark has changed.
And the quiet one
If you’ve been wondering about it for weeks, it’s reasonable to have it looked at rather than keep wondering.
08 · Next steps
Getting it checked
A podiatry check for a black toenail is quick and hands-on.
We’ll ask how and when it started, look closely at the nail and the skin around it, and check your shoes, lacing and nail length. If running is part of the story, we’ll look at how your foot moves too. Then we’ll explain what we found in plain English: a bruise to let grow out, a nail worth testing for fungus, or something your GP should see.
What to bring
- Your grow-out photos, with dates
- The shoes you were wearing when it happened, plus your usual running or walking shoes
- A list of any medicines you take
- Notes on any knock, race or long walk before it appeared
Good to know
You don’t need a GP referral to see a podiatrist. If anything about the nail suggests it needs a dermatologist’s opinion, we’ll tell you plainly and suggest you see your GP, who can refer you on.
Offer for guide readers
- A close look at the nail and the skin around it
- A fit and lacing check of your own shoes
- Advice on caring for the nail while it grows out
- A plain-English plan, which may simply be to let it grow out
If you have any of the warning signs in section 07, please see your GP first.
Terms: $85 initial podiatry consultation (standard fee $110). Quote NEW85 when booking. Valid 14 days from download. New patients only, one per person, not with any other offer. Nail procedures, pathology tests, orthotics and follow-up visits are charged separately. HICAPS rebates claimable on the spot where your cover includes podiatry.
About
Nicole Hardidge & Bellevue Podiatry
Nicole is the Principal Podiatrist at Bellevue Podiatry in Rosanna. She completed her Bachelor of Podiatry at La Trobe University in 2009 and has spent more than fifteen years working with feet and lower limbs across Melbourne’s north-east.
- Address
- 8 Bellevue Avenue, Rosanna VIC 3084, a short walk from Rosanna station
- Phone
- (03) 9457 2336
- Appointments
- Six days a week including Saturdays. No GP referral needed.
- Health funds
- HICAPS on the spot. GP Medicare care plans, TAC and NDIS accepted.
Where the facts come from
Sequeira Campos MB, Launico MV. Subungual Hematoma Drainage. StatPearls, updated June 2025.
DermNet. Subungual haemorrhage (2020) and Acral lentiginous melanoma (2023).
Levit EK, et al. The ABC rule for clinical detection of subungual melanoma. J Am Acad Dermatol 2000;42(2):269–274.
Yaemsiri S, et al. Growth rate of human fingernails and toenails in healthy American young adults. J Eur Acad Dermatol Venereol 2010;24(4):420–423.
bpacnz. Fungal nail infections (2025).
Australian Podiatry Association. Shopping for correctly fitting shoes.
Kaiser Permanente. Toenail or fingernail avulsion: care instructions.
This guide provides general information only and is not a diagnosis. No written check can replace an examination by a registered health practitioner. If you have any of the warning signs above, please see your GP.