Like all medicines, finasteride can cause side effects in some people, although not everyone gets them.
Common side effects
These common side effects of finasteride happen in more than 1 in 100 people.
They usually improve after a while. There are things you can do to help cope with them:
Problems getting an erection and less interest in having sex
These side effects should improve with time. If they do not get better, speak to your doctor.
Problems with ejaculating, such as little or no semen
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.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
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.
Call your doctor or call 111 now 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)
Immediate action required: Call 999 or go to A&E now if:
- you have thoughts of harming yourself
Serious allergic reaction
In rare cases, finasteride may cause a serious allergic reaction (anaphylaxis).
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Other side effects
These are not all the side effects of finasteride. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.