What finasteride is for

Finasteride is used to treat an enlarged prostate.

It's also used to treat hair loss in men, but this is not available on the NHS. Finasteride for hair loss is only available with a private prescription, so you'll need to pay for the full cost of the medicine.

Finasteride works by lowering the amount of a hormone in your body called dihydrotestosterone. This helps to reduce swelling in your prostate, if you're taking it for an enlarged prostate. It can also help reduce hair loss in men.

How to take finasteride

Finasteride usually comes as tablets you swallow.

How much you need to take and for how long depends on your symptoms. Most people need to take finasteride once a day. You'll usually need to take it for 3 to 6 months before your symptoms improve.

When taking finasteride tablets:

swallow them whole with a drink of water
try to take them at the same time every day
take them with or without food

Always check the packet or leaflet that comes with your medicine. Ask a pharmacist or doctor for advice if you're not sure how to take it or have any problems taking it.

While taking finasteride you'll usually need to have regular check-ups to find out how well it's working.

If you need a PSA test while taking finasteride, tell your doctor because it can affect the result of the test.

Important: Use contraception

It's important to use contraception, such as condoms, while taking finasteride if your sexual partner is pregnant, or there's a chance they could get pregnant.

This is because finasteride passes into your semen and can cause problems with how a baby's genitals develop during pregnancy.

If you miss a dose of finasteride

If you forget to take a dose of finasteride, take the next dose when you remember, unless it's nearly time for your next dose.

If it's nearly time for your next dose, skip the dose you missed and take the next dose at the usual time.

Do not take 2 doses to make up for a missed dose.

If you take too much finasteride

Taking an extra dose of finasteride is unlikely to cause problems but it's important to get medical advice because if you take too much it can sometimes be dangerous.

Taking more finasteride than you've been prescribed will not increase its effect or make it work faster.

Urgent advice: Speak to a pharmacist as soon as possible if:

you've taken more than your prescribed dose of finasteride

If you're unable to speak to a pharmacist, or you took too much of your medicine on purpose, call NHS 111 for advice.

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If you're told to go to A&E, do not drive. Ask someone to drive you or call 999 and ask for an ambulance.

Bring the finasteride packet or leaflet inside it, any remaining medicine, and any other medicines you take.

Side effects of finasteride

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

Side effects of finasteride include:

erection problems (erectile dysfunction)
low sex drive (loss of libido)
problems ejaculating
infertility after long-term use

Finasteride will not usually affect your ability to drive, ride a bike or use machinery.

Non-urgent advice: Speak to a pharmacist or doctor if:

you have any side effects that bother you or do not go away

They may be able to give you advice about how you can reduce the side effects. Keep taking your medicine unless you're advised to stop.

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Serious side effects

Finasteride can sometimes cause serious side effects, although most of them are rare.

Possible serious side effects of finasteride include:

an allergic reaction (anaphylaxis) – which can cause symptoms such as a swollen throat or tongue, a raised, itchy rash or difficulty breathing
depression or suicidal thoughts
feeling your heart beating or like your heart has skipped a beat (heart palpitations)
blood in your semen

Immediate action required: Call 999 if:

you're taking finasteride and think you might be having anaphylaxis

If you think you're having any other serious side effect, call NHS 111.

There's also an increased risk of breast cancer if you take finasteride for a long time. Your doctor will talk to you about the risks and benefits.

It's important to see your GP if you notice any lumps, nipple discharge or changes in your breasts, or have other symptoms you're worried about.

More about side effects

These are not all the side effects of finasteride.

For a full list, see the leaflet that comes with your medicine or search for your medicine leaflet on the electronic medicines compendium website.

You can report any side effects you get on the Yellow Card website

Who can and cannot take finasteride

Most adult men can take finasteride.

But finasteride is not suitable for everyone. For example, it may not be suitable if:

you've had an allergic reaction or other serious side effect from finasteride
you have a blockage in your urinary tract (kidneys, bladder or urethra)
you have liver problems

Before taking finasteride, tell your doctor if you have any medical conditions.

Finasteride is not prescribed for women. If you're pregnant you should not touch broken or crushed finasteride tablets. Get advice from a GP or pharmacist if you're pregnant and have touched or swallowed finasteride.

Taking finasteride with other medicines, food and drink

There are some medicines, remedies and supplements that may not mix well with finasteride.

This includes:

other medicines containing finasteride
dutasteride

Before taking finasteride, tell your doctor if you're taking any other medicines, herbal remedies, vitamins or supplements.

Finasteride - Common brands: Propecia