Propecia (Finasteride)

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Medically reviewed by
Dr Daniel Atkinson
GP Clinical Lead
on August 02, 2022.
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Common side effects of Finasteride

The first thing you should know about what side effects you might expect to get from medicines like finasteride is that there is a strict system in place that categorises how common it is for people to experience them. This classification goes from ‘very common’ (more than 1 in 10 people will get this side effect) to ‘very rare’ (less than 1 in 10,000 people will get this side effect).

Here’s the classification in full:

  • Very common: more than 1 in 10
  • Common: 1 in 100 to 1 in 10
  • Uncommon: 1 in 1,000 to 1 in 100
  • Rare: 1 in 10,000 to 1 in 1,000
  • Very rare: less than 1 in 10,000.

So, officially speaking, there aren’t actually any common side effects of finasteride for hair loss. Any side effects reported from this treatment are experienced by less than 1 in every 100 people.

With that in mind then, the most common side effects of Finasteride and Propecia are as follows:

  • difficulty getting or keeping an erection
  • lower sex drive
  • difficulty ejaculating, such as a decreased amount of semen during ejaculation (this won’t stop you having sex normally)
  • depression.

These four side effects are all classed as uncommon, with up to 1 in 100 users experiencing them.

Rarer side effects of Finasteride include:

  • rash
  • palpitations
  • fast heartbeat
  • tenderness of the breast tissue
  • testicular pain
  • anxiety
  • changes in the way the liver is working, indicated by blood tests
  • persistent erectile dysfunction after discontinuation of treatment
  • persistent lowered sex drive after discontinuation of treatment
  • persistent problems ejaculating after discontinuation of treatment
  • infertility, usually in men with other fertility risk factors. Fertility levels usually return to normal or improve once treatment is stopped. However, long term clinical studies into the area have not been carried out.

The frequency of these side effects is unknown, but they should be reported if they occur.

These side effects are very rare, but can be dangerous. If you experience any of them, stop taking Finasteride immediately and get medical help.

Signs of an allergic reaction:

  • swollen lips, tongue, throat or face
  • skin rashes, itching, or lumps under the skin

Signs of depression:

  • new or increased low mood
  • feeling sad or unworthy
  • thoughts of suicide

Signs of breast cancer:

  • lumps appearing in breast tissue
  • pain in breast tissue
  • breast tissue swelling or growing
  • discharge coming from the nipples.

Is Finasteride safe?

Finasteride is a licensed treatment for hair loss and side effects tend to be uncommon. This means that the regulatory agencies have decided it’s a safe treatment for hair loss after reviewing the evidence.

Lower sexual desire, struggling to maintain an erection and producing less semen than usual are some of the more common things people experience while taking Finasteride. Most of the side effects associated with finasteride stop once the treatment is no longer being used. But for a few men these side effects can continue for several months after the treatment has been stopped.

Finasteride is only available as a prescription treatment. This means that a clinician will need to make sure that it’s safe and the right treatment option for you before they prescribe it.

In some uncommon cases, taking Finasteride has been linked to feelings of depression. If you experience low mood after you start Finasteride, you should stop taking it immediately. Seek medical help, especially if you’re thinking of harming yourself.

Some people taking Finasteride find it harder to get or maintain an erection (ED). This might be because Finasteride reduces the levels of DHT in your body.

A 2021 meta-analysis of 73 different studies found that only 2.1% to 3.8% of people experienced sexual side effects when taking Finasteride. Of this small number, ED was the most common effect and usually got better by itself with time.

Some men taking Finasteride worry about their fertility. However, the actual risk seems to be low. A study on men taking 1mg of Finasteride per day for 48 weeks found there was no significant change in the numbers of sperm, their speed or their health. It’s also important to remember that fertility can decrease naturally as you get older.

If you already have poor fertility or you’re planning a family now, it might not be the best time to take Finasteride. Finasteride can reduce the amount of semen you produce, though studies suggest it will go back to normal when you stop taking the tablets.

Finasteride isn’t known to cause any eye problems. One study found that some people who had taken Finasteride also had vision problems. But the study only used a small number of participants and it didn’t come to the conclusion that there was a link between the two.

Finasteride has been shown to be an effective treatment for some patients with a rare eye disorder called central serous chorioretinopathy. But for most people, Finasteride won’t affect their eyes either way.

What about skin problems?

Finasteride has sometimes been linked to rashes or flushes. These are small, reddish areas on your skin or scalp that may sometimes be itchy. They should resolve on their own in a short time.

If a rash is very painful or itchy, growing in size or is accompanied by other worrying symptoms, you could be having an allergic reaction. Stop taking Finasteride and seek medical attention straight away.

High blood pressure hasn’t been reported as a risk of taking Finasteride. In fact, because too much DHT is associated with pressure on the heart, Finasteride might lower blood pressure. Studies in mice have also shown Finasteride even lowered their blood pressure and improved their heart function.

Finasteride allergies are very rare, but allergic reactions to any substance are possible. If you’ve ever had an allergic reaction to Finasteride before, tell your doctor and don’t keep taking the medication. If you’ve had an allergic reaction to another medicine, tell your prescriber so they can help you decide if Finasteride is right for you.

Post-finasteride syndrome is a name given by some former users of Finasteride to experiences they’ve had after stopping treatment. Some of these people feel they have worse sexual and psychological health due to Finasteride, even years after they last used it.

Post-finasteride syndrome is a controversial term and it’s not recognised by the medical community. Current research has not found a link between Finasteride and these long term problems.

The International Society of Hair Restoration Surgery (ISHRS) made a task force to look into reports of post-finasteride syndrome. They put out a statement in 2011 that there was nothing to suggest a link between Finasteride use and long-term sexual side effects.

Sexual side effects after taking Finasteride have been reported by some people. However, this data is based on self-reported symptoms. Sexual problems, such as ED, are common and treatable.

Sexual side effects of Finasteride are also rare even during treatment. Further studies are being carried out into Finasteride to make sure its long-term safety is as strong as previous studies have indicated.

How can I know if Finasteride is safe for me to use?

care-iconAny side effects caused by Finasteride are uncommon and it’s a safe treatment for most men. As with any medication you should be aware of the possible side effects and watch out for them. If you experience

If you want to make sure Finasteride is the right choice for you, you can tell us about your health. One of our trained clinicians will check over your information and offer you the best hair loss treatment option for you. We can answer any questions you have and we’ll check in with you during treatment. anything that worries you, stop the medication and report the symptoms to your doctor.

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This page was medically reviewed by Dr Daniel Atkinson, GP Clinical Lead on August 02, 2022. Next review due on August 01, 2024.

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