Fungal nail infections: why treatment takes months

Medically reviewed by Muhammad A Jalil, Superintendent Pharmacist (GPhC Reg No: 2236161)

Published 2026-08-22 · Clinically reviewed 2026-08-22 · Updated 2026-08-23

Why fungal nail treatment takes months to show results, how tablets and lacquers compare, and how to stop the infection coming back once it clears.

Fungal nail treatment is slow for a reason that has nothing to do with the medicines: nails grow at a crawl, and a treated nail only looks normal once the damaged part has grown out and been replaced. Toenails take twelve to eighteen months to renew completely, so even a treatment that kills the fungus within weeks leaves you watching a discoloured nail shrink towards the tip for a year. Understanding that timeline is the difference between a cure and a drawer of abandoned bottles — and it is why the decision between tablets, lacquers and doing nothing deserves five minutes of honest thought before you start.

How to know it is actually fungus

A thickened yellow toenail is not automatically fungal — psoriasis, age-related thickening and old trauma mimic it, and studies suggest up to half of suspected fungal nails are something else. Classic fungal features: the nail turns white-yellow or brown at the free edge first, thickens, turns crumbly underneath, and the change creeps towards the base over months, often starting in the big toe and often alongside athlete's foot between the toes.

Because oral treatment runs for months, UK practice is to confirm the diagnosis before tablets — a nail clipping sent for microscopy and culture through your GP, or dermatophyte testing arranged privately. Treating a non-fungal nail with months of antifungals helps nobody.

Your three real options

Do nothing — legitimately. A painless fungal nail in an otherwise healthy person is a cosmetic problem. If it does not bother you, leaving it is a valid choice; keep it trimmed and watch for spread. The infection rarely clears itself, but it also rarely causes harm in healthy people. The calculation changes with diabetes, peripheral vascular disease or a weakened immune system, where skin cracks and secondary infection carry real risk — treat, and involve your GP or podiatrist.

Nail lacquer for mild disease. Amorolfine 5% lacquer, applied once or twice weekly after filing the nail surface, suits infections limited to the outer edge and under half of one or two nails, without base-of-nail involvement. It demands patience and consistency: six months for fingernails, nine to twelve for toenails, with complete-cure rates in the modest 15–30% range. Its virtues are safety and no interactions.

Tablets for anything more. Oral terbinafine is the standard UK choice: 250 mg daily for six weeks for fingernails, twelve weeks (sometimes up to six months) for toenails. It travels via the nail bed into the growing plate and keeps working after the course ends. Cure rates are the best available — mycological cure around 70–80%, visually normal nails somewhat lower — precisely because the medicine reaches where lacquers cannot. Itraconazole, often as monthly "pulse" courses, is the alternative when terbinafine is unsuitable.

Terbinafine is generally well tolerated; the famous quirk is taste disturbance (food tasting flat or metallic — reversible, but report it), and the caution that matters is the liver: pre-existing liver disease usually rules it out, clinicians may check liver blood tests around longer courses, and dark urine, pale stools or yellowing skin during treatment means stop and seek advice. It also interacts with some antidepressants, beta-blockers and tamoxifen — a medication review is part of any responsible prescription.

If a spreading or unsightly nail has you ready to treat it properly, you can check your eligibility for fungal nail treatment online — a UK clinician reviews photos and your history, confirms whether testing is needed first, and prescribes the option that matches how much nail is involved.

The long middle: what progress looks like

Mark the boundary between healthy and damaged nail with a fine file line (or photograph it monthly against a ruler). Success looks like clear nail advancing from the base while the damaged zone drifts outward — about 1 mm a month on toes. The damaged part never "heals"; it gets replaced. Expect a toenail to look respectable around month nine and normal somewhere between months twelve and eighteen. Judge the treatment at the base of the nail, not the tip.

Stopping it coming back

Reinfection, not treatment failure, explains many "relapses" — your shoes and shower floor are still seeded with the fungus that started it:

Treat athlete's foot promptly and permanently — it is the usual source. Antifungal cream for the skin is quick; keep some in the cabinet.
Rotate and air shoes; use antifungal powder or spray inside pairs you wore during the infection.
Keep nails short and dry; separate nail tools for the affected nail during treatment, and disinfect clippers.
Flip-flops in communal showers, gyms and pool changing rooms.
Wash socks hot, and change them daily (breathable fibres help sweaty feet).

Frequently asked questions

Can I just paint over it while it grows out?

Cosmetic polish is fine over a nail being treated with tablets. With amorolfine lacquer, polish on top is generally discouraged — it interferes with the medicated layer. Either way, give the nail polish-free spells so you can track the grow-out line.

Why did my nail not improve after the tablets finished?

Often it did — just invisibly. Terbinafine keeps killing fungus in the nail for months after the last tablet, and the visual verdict belongs at month nine to twelve, not week twelve. True failure (no clear nail advancing from the base by around six months post-course) points to re-testing, a resistant organism, a different diagnosis, or a switch of drug.

Are laser treatments worth it?

Evidence so far is underwhelming: temporary cosmetic improvement in some studies, but cure rates well below tablets and no UK guideline backing. By all means research, but be sceptical of clinic before-and-after photos taken inside the natural grow-out window.

Is a fungal nail contagious to other people?

Mildly, via shed skin and nail debris in warm damp places — the same route athlete's foot takes. Household members should not share towels, clippers or shoes with you, and the flip-flop rule protects the gym as much as it protects you.