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5 minute read · Last reviewed 22 October 2026

Terbinafine and other tablets for fungal nails: what to expect

Terbinafine is a once-a-day antifungal tablet and the usual first choice in the UK for a confirmed fungal nail infection that has spread beyond the tip of the nail. A course is six weeks for fingernails and three to six months for toenails, and trials show it clears the fungus in around three in four people, the best rate of any treatment. It is prescription-only, needs a confirmed diagnosis, and GPs often check liver function with a blood test.

Why tablets rather than a paint?

A paint-on treatment has to get through the nail plate to the fungus living underneath it, which it does poorly once more than the tip is involved. Tablets reach the nail bed from the inside through the bloodstream and become concentrated in the growing nail, so the new nail that grows out is protected while the old infected nail is pushed off the end. For an infection involving half the nail or more, or several nails, tablets are the only treatment with a good chance of cure.

Before you start

A nail sample. NICE and the NHS advise sending nail clippings to a laboratory before prescribing tablets. Terbinafine works against dermatophyte fungi, which cause most infections, but not reliably against yeasts, and it does nothing for psoriasis or injury. The test takes two to three weeks and avoids months of pointless tablets.

Questions your GP will ask. Whether you have ever had liver or kidney problems; what other medicines you take (terbinafine interacts with some antidepressants, beta-blockers and other drugs); whether you are pregnant, planning pregnancy or breastfeeding; whether you have psoriasis or lupus, which terbinafine can occasionally worsen.

A blood test. Many GPs check liver function before the course and again after four to six weeks, particularly for courses longer than six weeks. Not every practice does; the NHS website says a GP “may” order it.

The course

  • Dose: 250 mg once a day, with or without food.
  • Fingernails: six weeks.
  • Toenails: twelve weeks as a minimum, often extended to six months for a big toenail or a slow-growing nail. Your GP will tell you the length when prescribing.
  • If you miss a dose: take it when you remember unless the next one is due; do not double up.

Itraconazole, the main alternative, is usually taken as “pulses”: 200 mg twice a day for seven days, then three weeks off, repeated for two pulses (fingernails) or three (toenails). It is preferred for yeast infections and for some people who cannot take terbinafine, but it interacts with many medicines and is not suitable for people with heart failure.

What to expect month by month

  • Month 1. Nothing visible. Side effects, if any, usually appear now: stomach upset, headache, a rash, or a change in taste.
  • Months 2 to 3. A band of clear, healthy nail appears at the base and grows outwards. This is the sign the treatment is working. The infected end looks the same.
  • End of course (3 to 6 months). Perhaps a third to a half of the nail is clear. The tablets stop; the fungus should be dead, but the damaged nail is still there.
  • Months 6 to 12. The clear nail keeps growing out. Keep the nail short, keep feet dry, treat any athlete’s foot.
  • 12 to 18 months. A big toenail is fully replaced. This is when “cure” can be judged.

If no clear band has appeared at the base by the end of the course, go back to the GP; a repeat sample may be needed and the diagnosis reconsidered.

How well does it work?

In trials, terbinafine clears the fungus on laboratory testing in around three in four people with toenail infection, and produces a fully normal-looking nail in roughly half to two-thirds. Itraconazole’s rates are a little lower. Those are better figures than any other treatment, but they also mean one in four people is not cured by a first course, and some need a second course or a combination with a paint-on treatment or nail removal.

Relapse and reinfection are common in the years after a successful course. Treating athlete’s foot promptly, keeping feet dry and replacing or disinfecting old shoes reduce the risk.

Side effects

Common (up to one in ten): headache, feeling sick, bloating, diarrhoea, indigestion, loss of appetite, a mild rash, aching joints or muscles.

Uncommon: loss or change of taste or smell, which usually recovers within weeks of stopping but can take longer; depression or low mood; hair thinning.

Rare but serious: liver injury (dark urine, pale stools, yellow skin or eyes, severe tiredness, pain under the right ribs); severe skin reactions (a spreading rash, blistering, peeling, mouth ulcers); a drop in blood cell counts (unusual bruising, bleeding, fever, sore throat). Stop the tablets and see a doctor straight away.

Report side effects to the MHRA through the Yellow Card scheme.

Who should not take terbinafine

  • People with liver disease, or with abnormal liver function on the blood test.
  • People with severe kidney disease (a lower dose may be possible).
  • Pregnant or breastfeeding women, unless the GP judges the benefit outweighs the risk; usually treatment is deferred.
  • Children, for whom it is not licensed in the UK for nail infection.
  • People with psoriasis or lupus should discuss it, as flare-ups have been reported.

Cost

On the NHS in England, the standard prescription charge per item applies; a course may need two or three prescriptions. Prescriptions are free in Scotland, Wales and Northern Ireland. Privately, a GP or online prescriber consultation plus the tablets is usually under £50 for a course, as terbinafine is a cheap generic.

Combining tablets with other treatment

Many podiatrists recommend thinning the thick nail (which the typical fungal nail appointment, from £48 across clinics listed on this site, includes) so that the dead infected nail is removed faster and the new nail can be seen. Combining tablets with a paint-on antifungal or laser is common for severe infections. Our guide to fungal nail treatment options compares everything.

Getting a prescription

See your GP, who will arrange the nail sample and the blood test. Some podiatrists are independent prescribers or work with a prescriber and can arrange tablets privately. Our guide to fungal nail infection on the NHS explains what the GP route involves, and the listings on this site show podiatry clinics near you; 640 listed clinics say they treat fungal nails.

Sources

Common questions

How long do you take terbinafine for toenail fungus?

Usually three to six months, one 250 mg tablet a day. Fingernails need six weeks. The nail keeps improving for months after the course ends, because the fungus has been killed but the damaged nail has to grow out.

Does terbinafine damage your liver?

Rarely. Serious liver problems are very uncommon but have happened, so GPs often check liver function with a blood test before starting and again after four to six weeks. Stop and see a doctor straight away if you develop dark urine, pale stools, yellow skin or eyes, or feel very unwell.

Why have I lost my sense of taste on terbinafine?

Loss or change of taste is a known side effect, affecting a small proportion of people. It usually returns within weeks of stopping, though in rare cases it takes months. Tell your GP; they may stop the course.

Can I drink alcohol on terbinafine?

There is no direct interaction, but because terbinafine can affect the liver, most doctors advise keeping alcohol to a minimum during the course. Ask your GP if you drink regularly.

What should you not do while taking terbinafine?

Do not stop early because the nail looks no different; the fungus is cleared long before the new nail grows out. Avoid heavy drinking, because the tablets are processed by the liver. Tell the prescriber about other medicines, as terbinafine interacts with some antidepressants, beta blockers and other drugs. And report a rash, yellowing skin or eyes, dark urine, pale stools or a loss of taste or smell straight away.

Is it worth taking terbinafine for toenail fungus?

For a confirmed infection it is the treatment NICE recommends first, because it clears the fungus in more people than any paint or cream. The trade-off is a course of three to six months, blood tests in some cases and the side effects above. Whether that trade-off is worth it depends on how many nails are affected, how much the nail bothers you and your other health conditions, which is a conversation for a GP or podiatrist.

How long does terbinafine take to work?

The tablets start killing the fungus within days, but the nail only looks better as it grows out, so the first clear nail appears at the base after two to three months and a toenail takes 12 to 18 months to look normal. The course itself is usually 12 weeks for toenails and 6 weeks for fingernails.

Can terbinafine cause weight gain?

Weight gain is not a listed side effect in the UK product information. Loss of taste or smell is, and it can change appetite in either direction while it lasts; it usually recovers after the tablets stop. Report any taste change to the prescriber, because the advice is to stop the course if it happens.

Is terbinafine safe?

For most adults, yes, and it has been prescribed for decades. The main cautions are liver problems, which is why some GPs check liver blood tests before and during a course, and interactions with some antidepressants, beta blockers and heart rhythm medicines. It is not recommended in pregnancy or breastfeeding or for people with liver disease.

Is terbinafine an antibiotic?

No. Terbinafine is an antifungal: it kills fungi by blocking an enzyme they need to build their cell walls, and it has no effect on bacteria. That is why it does not treat a bacterial nail infection, and why a nail clipping is tested first.

Can you buy terbinafine over the counter?

The cream and gel for athlete's foot, yes, from any pharmacy. The tablets used for fungal nails are prescription-only in the UK, from a GP or a registered online prescriber after a consultation.

How long does terbinafine stay in your system?

It builds up in the skin and nails and stays there for weeks after the last tablet, which is part of why it works. Most of a dose leaves the blood within a few days, but traces in the nail and skin are measurable for months; that is harmless and is what keeps protecting the new nail as it grows.

What should you not take with terbinafine?

Tell the prescriber about every medicine. Terbinafine interacts with some antidepressants (tricyclics, SSRIs), beta blockers, antiarrhythmics such as flecainide and propafenone, codeine and tamoxifen, by changing how the liver processes them; the dose of the other medicine may need adjusting. Avoid heavy alcohol during the course.

Can you take cephalexin and terbinafine together?

There is no known interaction between the two, so they are commonly taken together when someone has a bacterial infection as well as a fungal nail. Check with the prescriber or pharmacist all the same, because the answer depends on what else you take.

This guide is general information, not medical advice. Speak to a qualified professional about your own situation.

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