Thick toenails

What are thick toenails, and how common are they?

Thick toenails (onychauxis) are nails that grow abnormally thick. Over time they may curl and turn white or yellow¹. They're most often seen in the toenails of older people², and toenails are affected more than fingernails³.

Some thickening is a normal part of ageing. Nails grow more slowly, become brittle, and often thicken and change colour³. Nail problems usually aren't caused by anything serious⁴. Thickening can also have other causes, so it helps to know what they are.

It can help to note when the thickening started, which nails are affected, and any colour change, injury or new shoes. Share this with your podiatrist or GP.

What causes thick toenails?

The commonest causes are fungal infection, ill-fitting shoes, injury, psoriasis (a skin condition that can affect nails), reduced circulation and diabetes. It can also run in families¹. Long-term ill-fitting footwear and neglected nails are linked with thicker toenails².

A fungal infection makes the nail thick, crumbly and discoloured, most often in the big toenail². Toenails get fungal infections much more often than fingernails, partly from shoe pressure and circulation problems⁵. Infection is more likely with diabetes, psoriasis, poor circulation or a weakened immune system⁶.

These causes are hard to tell apart by looking. Psoriasis can't easily be told from a fungal infection², and injury from shoes can look like one too⁶. Testing nail clippings is what separates them⁷.

How do I find out what's causing it?

A podiatrist or GP will ask about your history, such as psoriasis, injury, nail problems in the family, diabetes, circulation and immune health⁷. They'll also examine your nails. Looking alone can't reliably show the cause, and it's the method most likely to wrongly label a nail as fungal⁵.

To check for fungus, nail clippings and debris from under the nail are sent to a laboratory⁶. It's best to do this before any long-term treatment starts⁸. A single negative result doesn't always rule out infection⁹.

Testing matters because treating a look-alike condition as a fungal infection can mean the wrong diagnosis, unwanted side effects and the problem getting worse⁷.

What can I do at home first?

Regular cutting and filing reduce the thickness and can ease discomfort and improve how the nail looks¹. Try gently filing across the thickened part of each nail 2–3 times a week, when the nail is dry, before a bath or shower¹⁰. Filing downwards, away from your body, once a week can help keep the length and thickness steady. Ask someone to help if you need to¹⁰.

Wearing well-fitting shoes is also sensible, since long-term ill-fitting footwear is linked with thicker toenails².

If your nails are too tough to cut or you can't reach them, a podiatrist can help with trimming, shaping and nail care³⁴. These simple steps are the place to start. Antifungal treatment is for when testing has confirmed a fungal cause⁷.

What helps if that isn't enough?

If testing confirms a fungal infection, antifungal treatment can be added. Medicated nail lacquers and solutions can help, but they clear the infection in relatively few people, and some cause mild skin reactions where they're applied¹¹.

Antifungal tablets clear the infection better than dummy tablets¹². They tend to have higher cure rates than treatments applied to the nail, but more significant side effects¹³. If a lacquer or cream hasn't worked, your GP can talk through tablets. A blood test to check your liver is needed first¹, and your other medicines should be reviewed⁷.

These treatments are aimed at clearing the fungus. How much they thin the nail isn't clear yet.

For children, tablets are considered only for moderate to severe infection, or long-lasting infection where treatment on the nail hasn't worked. They need regular blood checks¹⁴.

Will it get better, and can I stop it coming back?

It isn't clear how often thickened nails return to normal or come back. Try not to assume a thick nail will clear or stay clear. Thickening is common with ageing, so it may need ongoing attention³. Keeping up regular nail care and wearing well-fitting shoes are sensible habits.

If you have diabetes, poor circulation or a weakened immune system, fungal nail infection is more likely⁶. For people with diabetes, experts recommend preventive foot care alongside nail treatment, with advice on footwear and foot care¹⁵. Ask your GP or podiatrist about this. See your GP or a podiatrist if a nail changes or the thickening comes back.