About finasteride

Finasteride is used to treat men with an enlarged prostate (benign prostate enlargement). It can help ease your symptoms if:

  • it's difficult to start peeing
  • you need to pee urgently or frequently more often
  • it's difficult to empty your bladder completely

Finasteride comes as tablets. It's available on prescription only.

It can also be used to treat men for hair loss (male pattern baldness).

However, for hair loss you can only get finasteride on a private prescription. This means you'll need to pay the full cost of the medicine.

This medicine is generally not recommended for women. It might be prescribed by a specialist doctor only in very rare cases.

Key facts

  • You'll usually take finasteride tablets once a day.
  • The main side effects are losing interest in sex and difficulty getting an erection.
  • Finasteride can affect the results of PSA testing (a blood test to check for prostate cancer)
  • This medicine gets into semen and can harm an unborn baby. Use a condom when having sex if your partner is pregnant or could get pregnant.
  • If you're pregnant or trying to get pregnant, do not touch crushed or broken finasteride tablets. If the tablets are broken, the medicine can pass through your skin and can harm your baby.

Who can and cannot use finasteride

Finasteride can be taken by men aged 18 years or over.

It's generally not recommended for women or children.

Finasteride is not suitable for some people. To make sure this medicine is safe for you, tell a doctor if you:

  • have had an allergic reaction to finasteride or any other medicines in the past
  • have severe bladder problems
  • have liver problems
  • are trying for a baby or have a pregnant partner – this medicine passes into semen and can affect an unborn baby

How and when to take finasteride

You can take finasteride with or without food. It does not matter what time of day you take it, just make sure it is around the same time each day.

Swallow your finasteride tablets whole with a drink of water. Do not break or crush them.


Pregnant women must not touch crushed or broken finasteride tablets. This medicine passes through skin and can harm an unborn baby.


For enlarged prostate the usual dose is 5mg, taken once a day.

For hair loss, the usual dose is 1mg, taken once a day.

You will usually take finasteride for a long time. You may need to take it for several months or years.

What if I forget to take it?

If it's less than 6 hours since you were due to take it, take your finasteride as soon as you remember.

If it's more than 6 hours since your dose was due, skip the missed dose and take the next one at the usual time.

Do not take a double dose to make up for a forgotten dose.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Finasteride is generally very safe. Taking too much is unlikely to harm you.

Call your local emergency service if:

  • you take too much finasteride and feel unwell

Side effects

Like all medicines, finasteride can cause side effects in some people, although not everyone gets them.

Common side effects

These common side effects happen in more than 1 in 100 people.

They usually improve after a while. However, talk to your doctor or pharmacist if these side effects bother you or do not go away:

  • problems getting an erection and less interest in having sex
  • problems with ejaculating, such as little or no semen

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people. Some people may notice these side effects after taking finasteride for a few months.

Speak to your doctor if you get:

  • any lumps, pain or swelling in your chest area or discharge from your nipples – these may be signs of a serious condition such as breast cancer
  • unusually low mood (depression) or thoughts of harming yourself

Serious allergic reaction

In rare cases, finasteride may cause a serious allergic reaction (anaphylaxis).

Call your local emergency service if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you are wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of finasteride. For a full list see the leaflet inside your medicines packet.

How to cope with side effects

What to do about:

  • problems getting an erection and less interest in sex – these side effects should improve with time. If they do not get better, speak to your doctor.
  • problems with ejaculating – if the amount you ejaculate is less than usual or you have no semen at all, you do not need to worry as this side effect is harmless. Talk to a doctor if it does not get any better.

Advice for women

Even though finasteride is not generally prescribed for women, it could still harm an unborn baby.

Use a condom when having sex if your partner is taking finasteride. This is because small amounts of finasteride pass into semen.

Do not touch any crushed or broken finasteride tablets if there's any chance you could be pregnant. Finasteride can get into your bloodstream through your skin if you handle broken tablets. This is why the tablets come with a protective coating.

Cautions with other medicines

Finasteride is not affected by other medicines.

Mixing finasteride with herbal remedies and supplements

St John's wort (a supplement sometimes taken to help with depression) might stop finasteride working as well as it's supposed to.

However, there's very little information about taking other herbal medicines and supplements with finasteride.


Tell a doctor or pharmacist if you're taking other medicines, including remedies, vitamins or supplements.

Common questions about finasteride