Finasteride side effects 

Finasteride is a medication that can be used to treat hair loss, and is especially effective when used for male pattern baldness. It inhibits the enzyme that converts testosterone into dihydrotestosterone (DHT), which causes the growth phase of your hair follicles to gradually decrease until you no longer grow hair. By causing there to be less DHT present in the scalp, finasteride can prevent you from losing any more hair and, in some cases, encourage your hair to regrow.  

However, it can cause some side effects. We want you to feel confident when using the treatment. So, we’ve put together a guide covering what the side effects of finasteride are, including the difference between the 1mg and 5mg doses, and whether the side effects are permanent when you stop taking the drug.    

Side effects of the drug finasteride 

Finasteride side effects in women and men include:  

• low sex drive (libido) 

• erectile dysfunction (impotence)  

• ejaculatory disorders  

• breast swelling or tenderness (gynecomastia)  

• rapid heartbeat (heart palpitations) 

• pain in your testicles  

• anxiety 

• depression 

• chills 

• cold sweats 

• confusion 

• dizziness 

• skin reactions and itching 

• swelling of face, lips, tongue or throat, difficulty swallowing and breathing difficulties (angioedema) 

• changes in your liver function 

• blood in your semen 

• bloating or swelling of the face, arms, hands, lower legs, or feet 

How common are finasteride side effects? 

Most clinical trials report that finasteride is generally well tolerated, and side effects are relatively rare.  

Sexual side effects are the most common finasteride side effects in men, occurring in about 2.1–3.8% of individuals taking finasteride compared to a placebo. The different types of finasteride side effects within this category occur as follows:  

• erectile dysfunction (3.4–15.8%) 

• decreased sex drive (2.36–10%) 

• ejaculatory disorders (0.9–5.75%) 

Are side effects more common with 1mg or 5mg finasteride?  

Research does indicate a higher frequency of side effects when using 5mg per day of finasteride compared to 1mg per day. However, the usual dose of finasteride for hair loss is 1mg per day. 5mg per day is normally only prescribed to treat an enlarged prostate. As a result, side effects are less common when finasteride is prescribed to treat hair loss. 

What are the serious side effects of finasteride?  

Very rarely, serious side effects can occur after taking finasteride for a few months, such as:  

• lumps, pain or swelling in your chest area or discharge from your nipples (these may indicate breast cancer) 

• depression  

• suicidal thoughts  

You should make an appointment with your GP if you notice you are experiencing any of these symptoms. Because of the risk of suicidal ideation when taking finasteride, it is important to tell your family or friends that you're taking it so they can help you notice any changes in your mood. 

Finasteride can also sometimes cause a serious allergic reaction (anaphylaxis). You should call 999 if:  

• you suddenly experience swollen lips, mouth, throat or tongue  

• you're struggling to breathe or breathing very fast (it may 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 (this may be easier to see on the palms of your hands or soles of your feet if you have black or brown skin) 

• you suddenly feel 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 have a rash that's swollen, raised, itchy, blistered or peeling 

Who should avoid taking finasteride?  

You should check with your doctor before taking finasteride if you have: 

• previously had depression, or thoughts about harming yourself 

• severe bladder problems 

• liver problems 

• ever had an allergic reaction to any medication 

Are finasteride side effects permanent? 

In most cases, the side effects of taking finasteride will clear up after you stop taking it. This is because finasteride is designed to lower your DHT levels while you’re taking it, but if you stop taking it your DHT levels will return to their pre-treatment levels.  

However, very rarely, sexual side effects have persisted in patients even after they have stopped taking finasteride. This is known as post-finasteride syndrome.

FAQs 

Do finasteride side effects go away with continued use? 

Some studies have found that individuals who take finasteride long-term may experience a lower incidence of side effects over time. This means, for some people, they may just need to wait for their body to adjust to the medication. 

Why does finasteride cause sexual side effects?  

During puberty, DHT is involved in the development of: 

• facial hair 

• body hair 

• pubic hair 

• prostate growth 

In later life, it is involved in the maintenance of these characteristics. Reductions in DHT concentrations throughout your body can affect your prostate gland, genitalia (if you’re male) and brain. Some research has indicated that you may be more likely to experience finasteride side effects sexually if you have lower baseline levels of testosterone before taking finasteride.  

Additionally, DHT is thought to play a physiological role in the ability to get and maintain an erection by activating an enzyme that helps dilate (widen) blood vessels and increase blood flow to your penis.  

How to reduce side effects of finasteride 

If you are experiencing the side effects of finasteride, you should speak to your GP or a pharmacist about your next steps.  

You may be advised to try another course of treatment, such as minoxidil, based on your individual healthcare needs.  

A healthcare professional will be able to help you make the right decision for you.  

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