Nail Thickening

Skin and Nail Changes· Also known as: thick toenails, thickened nails, onychauxisUpdated Oct 2026

Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod, October 2026

At a Glance

Nail thickening means a fingernail or toenail grows thicker than usual, and it may curl or turn white or yellow. It is seen most often in the toenails of older people. Common causes include normal ageing, fungal infection, skin conditions such as psoriasis, injury, ill-fitting shoes and poor circulation. Several of these look alike, so a nail clipping test is often needed to find out whether a fungus is involved. Looking after the nail helps, and the right treatment depends on the cause.

What is it?

Nail thickening is when a fingernail or toenail grows thicker than it should. Over time the nail may also curl and turn white or yellow. The medical name is onychauxis.

It is seen most often in the toenails of older people, and toenails are affected more than fingernails. A thick nail can be hard to cut, and sometimes it makes walking uncomfortable.

Thickening is a sign, not a disease in itself. Sometimes it is simply part of getting older. Other times something is behind it that is worth finding and treating.

What can cause it?

Several things can thicken a nail. Some look very alike, so it can take a little detective work to find the one affecting you.

Fungal infection (onychomycosis): the nail becomes thick, crumbly and discoloured. It most often affects the big toenail.
Ageing: as we get older, nails grow more slowly and become brittle and prone to splitting. Discolouration and thickening are also common.
Psoriasis and other skin conditions: these can thicken the nail. Psoriasis in the toenails cannot easily be told apart from a fungal infection.
Injury and ill-fitting shoes: years of shoes that fit poorly, with repeated small knocks and pressure on the toes, can thicken a nail. This can also look like a fungal infection.
Reduced circulation or diabetes: both are among the common causes of thick nails.
Arthritis in the toes, or a change in the way you walk: both can be behind thickened nails.
Inherited conditions: some run in families, and some cause nail changes that look like a fungal infection.
Neglect of the nails: nails that have gone untrimmed for a long time can thicken, especially toenails in older people.

Who gets it?

Older people are at greater risk, and toenails are affected more than fingernails.

A fungal nail infection is more likely if you have diabetes, psoriasis, poor circulation or a weakened immune system. Fungal nail infection affects about 3 to 5 per cent of people in the general population. That isn't a figure for thick nails overall, and a thick nail is not always fungal.

If you have diabetes, vascular disease (problems with the blood vessels) or a weakened immune system, problems from a fungal infection are more common. In people with diabetes they can be serious for the foot. That is why nail changes in these groups are best checked early.

How is the cause found?

Your podiatrist or GP will start by asking when the thickening began, which nails are affected, and whether you have noticed colour changes, injuries or new shoes. They will also ask about psoriasis, diabetes, circulation and your immune system. Then they will look closely at your nails and feet.

Looking alone can't reliably tell the cause. A fungal infection in particular shouldn't be diagnosed by eye. The most reliable test is a laboratory test on a small clipping of nail, along with some debris from under it. Your practitioner may also use dermoscopy, which is a quick, painless look with a small magnifying device. It is a useful first step, but the laboratory test is still needed.

A single negative result doesn't always rule out infection, so your practitioner may weigh it up alongside what they see. If there is a dark band or another concerning sign, a small sample of the nail (a biopsy) may be needed.

Nail changes are not only a cosmetic matter. They can sometimes be a clue to illness elsewhere in the body. If the cause is unclear, it is worth getting it assessed.

Treatment

Treatment depends on the cause. If the thickening comes from ageing, pressure or neglect, looking after the nail itself is the main approach. If a fungal infection is confirmed, antifungal treatment is an option.

Looking after it at home

Regular cutting and filing reduces the thickness and can improve how the nail looks and feels. Gently file across the thickened part of each nail 2 to 3 times a week. The best time is when the nail is dry, before a bath or shower.

Once a week, file in a downwards direction, away from your body. This helps keep the length and thickness under control. Ask someone to help if you can't reach your feet comfortably.

Treatment from your podiatrist

Your podiatrist can trim and shape thick nails and care for toenails that are deformed or brittle. This is especially helpful if your nails are too tough to cut or you can't reach them. Regular professional care also helps pick up more serious nail problems.

Your podiatrist can arrange a nail clipping test if a fungal infection is possible. They can also talk with you about your footwear.

Other options

If a fungal infection is confirmed, a paint-on treatment is often tried first. A 10% efinaconazole solution clears the infection more often than a dummy solution. Mild skin reactions, such as irritation and small blisters, are slightly more common with it. Ciclopirox and tavaborole are other paint-on options. Complete cure rates with all of these are fairly low. They aim to clear the fungus, not to thin the nail, so it isn't clear how much a thick nail will improve.

If paint-on treatment doesn't work, your GP may prescribe antifungal tablets. Terbinafine is the preferred tablet, and it clears fungal toenail infection much more often than dummy tablets. Azole tablets also work, but terbinafine is probably better.

Tablets need some care. Severe liver injury from terbinafine is known but unusual. You will have a blood test to check your liver before starting, and again 4 to 6 weeks after starting. People with liver disease should only be given these tablets for strict reasons. Tell your GP about all your other medicines, as some can interact with them. If your immune system is weakened, you may need a different dose and length of treatment, with closer follow-up.

For children, tablets are considered only for moderate to severe infection, or infection that has lasted a long time after paint-on treatment hasn't worked. Because safety information in children is limited, blood tests are routinely used to monitor them.

Will it get better?

It isn't clear how long a thickened nail takes to recover or how often it comes back. So don't assume the nail will return to normal or stay clear. If it changes or comes back, have it looked at again.

When thickening is part of ageing, it tends to be ongoing. Regular care of the nails, including professional care, can keep it manageable.

Preventing it

No specific footwear, hygiene or nail routine has been shown to stop thickening or keep it from coming back. There are still sensible steps. Shoes that fit well are a good start, because long-term ill-fitting shoes are linked to thicker toenails. Regular nail care also helps.

If you have diabetes, foot care alongside nail treatment is recommended. Use your visits to get advice on footwear and foot care, and keep an eye out for drug interactions. If you have poor circulation or a weakened immune system, ask your GP or podiatrist about foot care and footwear too.

When to see a podiatrist

Book an appointment if

Your nails are too tough to cut or you can't reach them, a thick nail makes walking uncomfortable, or the look of your nails is upsetting you: book an appointment with your podiatrist. See your GP if you think a fungal infection or an underlying health condition may be behind the thickening. If you have diabetes, vascular disease or a weakened immune system, book early for any nail change.

Seek prompt assessment if

See your GP soon, without waiting to see if it settles, if you notice a single dark band on one nail, dark colour under the nail, or a 'bruise' under the nail with no known cause that doesn't grow out or go away. The same applies to a sore, growing, bleeding or discoloured area on the nail that isn't healing, or a dark band on a child's nail. A rare skin cancer can start in the nail. Most dark bands are harmless, but they should always be checked. Also see your GP soon if a nail changes shape or colour or falls off and you don't know why, if the skin around it becomes sore, red, swollen and warm, or if the thickening has no clear cause. If you have diabetes, vascular disease or a weakened immune system, see your podiatrist or GP soon about any nail change.

Frequently asked questions

Is a thick nail just part of getting older?

Often, yes. As we age, nails grow more slowly, become brittle and tend to thicken and change colour. This is normal and usually not serious. Still, thickening can have other causes, so if it has no clear reason or the nail changes, get it checked.

Do I need a test before using antifungal treatment?

Yes. Many nail problems look like a fungal infection, and the only reliable way to tell is a laboratory test on a nail clipping. Treating the wrong problem can lead to a wrong diagnosis, unwanted side effects and the real problem getting worse.