Side effects of finasteride

Finasteride is the generic version of branded Propecia – a prescription medicine used to treat hereditary hair loss (also known as male pattern baldness) in men aged 18 and over.

Finasteride can be privately prescribed by your GP or you can access it via Boots hair loss services, either online via the Hair Loss Online Clinic or in selected stores. You’ll only be offered treatment through our online clinic once you’ve completed an online consultation, or in store after having a consultation with a specially trained pharmacist (subject to clinician or pharmacist approval. Charges apply). This is to check that the medicine is suitable for you.

As with many medicines, finasteride has the potential to cause side effects. Side effects are unwanted symptoms caused by medical treatment.


Finasteride & pregnancy

Finasteride should not be taken by women. If you're pregnant, you should take extra care not to come into contact with the tablets, especially if they're crushed or broken, as finasteride has the potential to affect the development of your baby's sex organs.

If you accidentally come into contact with finasteride while pregnant, contact your GP or midwife for advice.

Finasteride isn’t suitable for men with partners who are pregnant or trying to get pregnant.


Finasteride & allergic reactions

An allergic reaction is when your body reacts to being exposed to a particular substance. The substance that causes the reaction is known as an allergen.

All the ingredients of finasteride tablets are listed on the label. If you know you have an allergy, check the label carefully to see if your allergen is listed. If it is listed, you should not take finasteride.

If you have a lactose allergy or intolerance, you may not be able to take finasteride, as the tablets often contain lactose.

As with taking any new medicine, you may find you have an allergic reaction to finasteride, even if you don't have a history of allergies.

Common symptoms of an allergic reaction include:

• Difficulty swallowing

• Swelling of your lips, tongue, throat or face

• Lumps or bumps under your skin (hives)

If you experience any of these symptoms, stop taking finasteride and contact your doctor immediately.

If you're experiencing swelling in your mouth or face that makes it hard to breathe, you should call 999 immediately.


Finasteride & feelings of depression

Some people who have taken finasteride have reported experiencing changes in their mood. These include feeling low in mood, experiencing depression, and developing suicidal thoughts.

If you experience any of these symptoms, stop taking finasteride immediately and make an urgent appointment to see your GP.

If you're feeling depressed or suicidal, it's very important to talk to someone. If you don't feel able to talk to friends or family about how you're feeling, you can call The Samaritans on 116 123. They're open 24 hours a day, every day.


Finasteride & changes to breast tissue

If you experience any of the following changes to your breast tissue while taking finasteride, you should stop taking it and see your GP immediately:

• Lumps in your breast tissue

• Breast tissue pain

• Discharge from your nipples

• Breast enlargement


These symptoms can be a sign of a serious condition, such as breast cancer. Remember that, while we usually think of breast cancer as a female disease, it can also affect men.


Other potential side effects of finasteride

The following side effects are classed as 'uncommon'. This means they're experienced by up to one in 100 men:

• You may find you're less interested than usual in having sex

• You may be unable to get or maintain an erection

• You may have problems with ejaculating – for example, you may find you ejaculate less semen than usual


There are also other side effects where the frequency isn't yet known:

• Heart palpitations (where you can feel your heartbeat)

• Swelling or tenderness in your breast tissue

• Pain in your testicles

• Changes in the way your liver's working – found by a blood test

• Difficulty in having an erection, even after you've stopped taking finasteride

• Being less interested in sex than before, sometimes even after you've stopped taking finasteride

• Anxiety

• Poor quality of semen, and/or male infertility


Before taking finasteride or any other medicine, you should read the patient information leaflet, where you'll find a full list of side effects.


How long will side effects last?

Side effects will generally go away once you stop taking finasteride.

If you experience side effects that carry on even after you've stopped taking finasteride, you should make an appointment to see your GP.


What should I do if I experience side effects?

If you think you're experiencing any side effects, tell your doctor or pharmacist. This includes any side effects that aren't listed on the patient information leaflet, but which you think may be caused by taking finasteride.

Your GP or pharmacist will report the side effects to the Medicines and Healthcare products Regulatory Agency (MHRA). The MHRA are responsible for licensing and monitoring all UK medicines and medical devices. This includes collecting and acting on reports of side effects experienced by people taking medicines. Reporting a side effect can help improve medicine safety for the future.

You can also report a side effect (or suspected side effect) directly to the MHRA yourself. Visit the MHRA website and follow the instructions.


Next steps

• If you think you're experiencing a side effect while taking finasteride, tell your GP or pharmacist. They will report your experience to the MHRA, who will use this information to help improve medicine safety in the future

• You can also report side effects directly to the MHRA by visiting the MHRA website