Quick answer: Most everyday nail changes are harmless. Vertical ridges, small white spots and peeling tips are usually caused by ageing, minor knocks or dry nails, not illness. Some changes are worth getting checked by a GP, though:
- A new or changing dark streak
- Thick, yellow or crumbly nails
- Nails lifting from the nail bed
- Pitting
- Deep horizontal grooves
- Spoon-shaped nails
- Persistently pale or blue nails
- Clubbing, where the fingertips swell and the nails curve over them
A new dark streak in one nail should be seen promptly. Blue nails with breathlessness or chest pain need emergency help.
This guide is general information, not medical advice. Nail changes have many possible causes, and only a doctor can diagnose them. If you're worried about any change, speak to your GP or pharmacist.
What healthy nails look like
Healthy natural nails are smooth, pinkish where they sit on the nail bed, firmly attached, and slightly flexible rather than brittle. Fingernails grow slowly, roughly 3mm a month, so a change you notice today often started weeks ago at the base of the nail. For how the nail is built, see our guide to nail anatomy.
Nail changes that are usually harmless
Vertical ridges
Fine lines running from the cuticle to the tip are very common, and they become more noticeable with age and when nails are dry. They're rarely a sign of illness. Don't try to buff them away, as that thins the nail. A ridge-filling base coat smooths the surface, and daily cuticle oil helps keep nails flexible. See our guide to cuticle oil and how nails change as we get older.
White spots
Small white dots or flecks (leukonychia) are usually caused by minor knocks to the nail. Common causes are tapping a desk, pressing too hard with a cuticle pusher, or peeling off gel or BIAB. Contrary to the popular myth, they aren't a sign of calcium deficiency. They grow out with the nail. If the whole nail turns white, or white spots keep appearing without any injury, mention it to your GP.
Peeling and brittle tips
Nails that split into layers at the tip, or snap as soon as they get any length, are usually dry. Frequent hand washing, cleaning products, water exposure, harsh filing and picking at gel are the usual causes. Wear gloves for cleaning, use cuticle oil daily, file gently with a fine 180/240 grit, and don't use your nails as tools. A layer of BIAB protects the free edge while weak nails grow. See nail file grits and repairing broken nails.
Yellow staining after polish
A yellowish tint after wearing dark polish, especially without a base coat, is usually staining from the colour pigments, and it grows out over time. This is different from thick, yellow, crumbly nails, which are covered below.
8 nail signs worth getting checked
1. A dark streak or band in the nail
A brown or black line running from the cuticle to the tip has many harmless causes. It's also common in people with darker skin tones, often in several nails. But a new dark streak in a single nail needs to be checked promptly by a GP, especially if it's getting wider or darker, has blurred edges, or the dark colour spreads onto the surrounding skin. Rarely, it can be a sign of melanoma under the nail, and early diagnosis matters. A dark spot that appears after trapping your finger is usually a bruise, and it should move towards the tip as the nail grows. If it isn't moving forward within a few weeks, or you can't remember an injury, get it checked. See a GP or urgent care quickly if it's very painful or covers a large part of the nail.
2. Thick, yellow or crumbly nails
Nails that become thick, discoloured (yellow, white or brown), brittle or crumbly, sometimes lifting at the tip, are most often caused by a fungal nail infection. It's more common in toenails. A pharmacist can recommend treatments for mild cases, and a GP can confirm the diagnosis and prescribe stronger treatment if needed. Treatment takes months, because the healthy nail has to grow out. If you have diabetes or a weakened immune system, or the infection is painful, spreading or not improving with treatment, see your GP (or podiatrist if you have diabetes) rather than self-treating. Don't apply gel, BIAB or polish over a nail you think is infected. Less commonly, yellow nails can be linked to other health conditions, so see a GP if the change doesn't have an obvious cause.
A green or green-black patch, often under lifted gel or extensions, is usually a bacterial infection, not mould. Remove the product and let the nail dry out. See a GP if the skin around the nail becomes red, swollen, hot or painful, or pus appears. See our guide to green nails ("greenies").
3. Nails lifting from the nail bed
When the nail separates from the skin underneath (onycholysis), the detached part looks white or yellow. Common causes include:
- Knocks to the nail
- Over-cleaning under the nails
- Aggressive manicuring
- Fungal infections
- Psoriasis
- A reaction to nail products
Keep nails short, avoid pushing tools under the free edge, and see a GP if it doesn't improve or there's no obvious cause. If it started after wearing gel, read allergic reactions to gel polish.
4. Pitting
Tiny dents in the nail surface, like the surface of a thimble, are often linked to skin conditions such as psoriasis or eczema, and sometimes to alopecia areata. If your nails are pitted, especially alongside patches of dry, scaly or itchy skin, mention it to your GP.
5. Horizontal grooves across the nail
Deep lines running across the nail from side to side (Beau's lines) appear when nail growth is temporarily interrupted. Common causes are a high fever, serious illness or surgery, certain medicines, or an injury to the nail. They grow out over a few months. If they appear without an obvious reason, or on several nails at once, see your GP.
6. Spoon-shaped nails
Nails that are thin and curve upwards at the edges, enough to hold a drop of water (koilonychia), can be a sign of iron-deficiency anaemia. Spoon-shaped nails can be normal in young children, but in adults, see your GP. A simple blood test can check your iron levels.
7. Very pale, white or blue nails
Nails that look very pale or white can be associated with anaemia or, less commonly, with liver or kidney conditions. Nails that look blue or purple can mean less oxygen is reaching your fingertips. Cold hands often cause a temporary blue tinge that goes away as you warm up. See your GP about nails that stay pale or blue. Get emergency help (call 112 or 999) if blue nails or lips come with breathlessness, chest pain or confusion.
8. Clubbing
Clubbing is when the fingertips become rounded and swollen, and the nails curve down over them. It usually develops slowly and can be linked to lung, heart or digestive conditions. It isn't something to treat cosmetically. If you notice it, see your GP.
Nail changes at a glance
| What you see | Usual cause | What to do |
|---|---|---|
| Vertical ridges | Ageing, dry nails | Cuticle oil and a ridge-filling base. See a GP if it's a single prominent ridge or split on one nail |
| Small white spots | Minor knocks | Let them grow out |
| Peeling, brittle tips | Dryness, water exposure, harsh filing | Gloves, cuticle oil, gentle filing |
| Yellow tint after dark polish | Pigment staining | Use a base coat. It grows out |
| New dark streak in one nail | Many causes, rarely melanoma | See a GP promptly |
| Thick, yellow, crumbly nails | Often fungal infection | Pharmacist or GP |
| Green patch under gel | Bacterial infection | Remove product, let it dry out, pharmacist if it doesn't clear |
| Nail lifting from the bed | Injury, infection, psoriasis, product reaction | GP if no obvious cause |
| Pitting | Often psoriasis or eczema | GP |
| Horizontal grooves | Illness, fever, injury | GP if no obvious cause |
| Spoon-shaped nails | Can be low iron | GP |
| Persistently pale or blue nails | Various | GP, or emergency help with breathlessness |
| Clubbing | Can be heart, lung or digestive conditions | GP |
If you wear gel or BIAB, check your bare nails
Gel polish and BIAB can hide what's happening underneath, so take a quick look at your bare nails each time you remove a set. Don't apply gel or BIAB over a nail that is lifting, discoloured, painful, or showing signs of infection. Give it time to recover, and get it checked if it doesn't improve. A lot of the damage blamed on gel comes from peeling it off or over-filing, so always soak it off properly. See how to remove gel polish at home and how to remove BIAB at home.
Everyday habits for healthy nails
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Moisturise daily. Massage cuticle oil into the cuticles and nails once or twice a day to keep them flexible.
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Protect them. Wear gloves for cleaning and washing up, and don't use your nails as tools.
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File gently. Use a fine grit, in one direction, on dry nails.
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Be gentle with cuticles. Push back lightly, never scrape the nail plate, and only trim dead skin. See cuticle pusher techniques.
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Never peel or pick off gel or BIAB. Soak it off properly instead.
- Eat a balanced diet. Nails need protein, iron and zinc like the rest of your body. Biotin supplements are often promoted for nails, but there's limited evidence they help unless you're deficient. They can also affect some blood test results, so tell your doctor if you take them.
For more, see the science of strong nails and why oil matters for the nail plate.
Frequently asked questions
What can your nails tell you about your health?
Most nail changes are cosmetic, but some can be a sign of a health condition. Examples include a new dark streak, thick yellow nails, pitting, spoon-shaped nails, persistently pale or blue nails, and clubbing. A GP can check whether a change needs investigating.
Are vertical ridges on nails a sign of illness?
Usually not. Vertical ridges are very common and become more noticeable with age and dryness.
Do white spots on nails mean a calcium deficiency?
No. That's a myth. White spots are usually caused by minor knocks to the nail, and they grow out.
What does a dark line on a nail mean?
Dark lines have many causes and are often harmless, especially if they appear in several nails in people with darker skin. A new dark streak in one nail, or one that is widening, darkening or spreading onto the skin, should be checked by a GP promptly.
What do yellow nails mean?
Thick, yellow, crumbly nails are most often a fungal infection. A light yellow tint after dark polish is usually staining.
What do spoon-shaped nails mean?
In adults, spoon-shaped nails can be a sign of iron-deficiency anaemia. See a GP, who can check your iron levels.
Can I wear gel or BIAB if I have a fungal nail infection?
No. Let the nail be treated first, and don't apply gel, BIAB or polish over a nail you think is infected.
When should I see a doctor about my nails?
See a GP if you notice a new or changing dark streak, thick or crumbly nails, lifting, pitting, horizontal grooves, spoon-shaped nails, persistently pale or blue nails, or clubbing, or if the skin around a nail is red, swollen and painful. Also see one about any change that doesn't have an obvious cause or doesn't grow out.
