Finasteride side effects: the serious risks
What the finasteride leaflet singles out as serious, whether those effects can outlast the tablets, and the steps you can take.
Taking finasteride (Propecia, Proscar), or worried about what it could do? Its serious side effects are sexual problems that can last after stopping, depression and suicidal thoughts. When problems carry on after the last tablet, it’s called post-finasteride syndrome (PFS).
The UK Propecia leaflet lists “persistent difficulty having an erection after discontinuation of treatment”.
So which warnings matter most, and what if the problems don’t stop?
What are the serious side effects of finasteride?
The leaflet’s most serious warnings are about sex, mood and breast changes. Finasteride lowers a hormone called DHT, which is how it slows hair loss and shrinks an enlarged prostate.
The UK Propecia leaflet lists lower sex drive, erection problems and less semen. It also lists persistent problems with sex drive, erections and ejaculation “after discontinuation of treatment”. Anxiety and pain in the testicles are listed too.
It asks men to report promptly “any changes in your breast tissue such as lumps, pain, enlargement or nipple discharge”, because these may be signs of a serious condition, such as breast cancer. Our article on finasteride and breast changes explains more.
Men with PFS also describe brain fog, poor sleep, tiredness and feeling emotionally flat. Our list of PFS symptoms goes through them.
Can finasteride cause depression or suicidal thoughts?
Yes, the leaflet says so. It says “depressed mood, depression and, less frequently, suicidal thoughts have been reported”. If that happens, it says to stop taking Propecia and contact your doctor.
PFS is more than sexual problems. Criteria proposed by doctors and researchers in 2022 also describe problems with cognition, depression and suicidal thoughts, which can happen with or without sexual changes.
In 2024 the MHRA, the UK medicines regulator, told prescribers to ask about any history of depression or suicidal thoughts before prescribing. Our article on finasteride and depression has the detail.
If you’re having those thoughts, call the Samaritans on 116 123, free, at any hour.
Dr Michael Irwig, a US hormone specialist, was one of the first doctors to study men whose side effects lasted. Watch this extract to hear why he thinks men should be told before they start. It’s background on the researcher, not proof of any figure here.
Can the side effects last after stopping?
For some men they do. The leaflet calls these problems persistent, and the MHRA says sexual problems “persisted even after treatment was stopped”. The 5 mg Proscar leaflet says the same about erections, sex drive and ejaculation.
For some people it has lasted years after stopping. Nobody knows yet who will be affected, or whether it will ease. Our article on recovery from PFS covers what’s known.
Tim took finasteride 5 mg a day for a prostate problem from 2008 to 2025. He says his sex drive and erections went soon after he started. He only made the link when the new warning card turned up in his box. In this extract he explains what that card changed, and why nothing had improved nearly a year after stopping.
Sexual side effects while taking finasteride are uncommon. In the trials behind the label, about 4 in 100 men on finasteride had them in the first year, against about 2 in 100 on a dummy tablet. They became less common over the next four years.
Nobody has measured how often problems last after stopping. Single reports to a regulator can’t give a rate, and many side effects are never reported. A low number of reports isn’t proof of safety. That’s why each report counts.
What can I do?
Finasteride helps many men keep their hair. If you have side effects, that’s a decision for you and your prescriber. If your mood drops, the Propecia leaflet says to stop taking it and contact your doctor as soon as possible.
Questions to take to your GP
An opening line: “Since I started finasteride, something has changed. Could the two be linked?”
- Could finasteride explain what I've noticed?
- What else should we rule out?
- The leaflet says some problems can persist after stopping. What does that mean for me?
- Will you report it as a Yellow Card, or should I?
Write down your dates: “Finasteride 1 mg from May 2022, last tablet June 2025. Lower sex drive since about March 2025.” Many people say it took time to be taken seriously. Bring the leaflet line.
Report it: it helps everyone
A doctor’s note helps you. A report to the medicines regulator helps everyone else: it is how patterns get noticed.
- No proof needed. A suspicion is enough, even years after stopping.
- Where: the Yellow Card scheme in the UK, MedWatch in the US. The MHRA asks you to say if a side effect “continued or started after treatment was stopped”.
- Use the right words. If symptoms continued after stopping, write Post 5-alpha-reductase inhibitor syndrome (MedDRA 10082430).
Our reporting guide walks you through it
What else do people ask?
Does Proscar 5 mg have the same risks? It’s the same medicine at a higher dose, for the prostate. Its leaflet lists sexual problems that may continue after stopping, and says to contact your doctor about mood changes. See Finasteride 5 mg (Proscar) side effects.
Is it riskier to buy finasteride online? The medicine is the same, but a quick online form may not cover the leaflet’s warnings. Read the leaflet and the card in the pack either way. Our article on buying from Hims, Keeps and Boots looks at this.
Do men with PFS share their stories? Yes. Many describe how it changed their work, relationships and health. You can read and watch them in our patient stories, and find others in the community.
Tim found the warning in his box after 17 years. If something has changed for you, write down the dates and report it. Our PFS page is a good place to start.
Sources
- Propecia 1 mg film-coated tablets, patient information leaflet, electronic medicines compendium (emc), last revised May 2026. Section 2: “Mood alterations such as depressed mood, depression and, less frequently, suicidal thoughts have been reported”; “stop taking Propecia and contact your doctor”. Section 4, frequency unknown: “persistent difficulty having an erection after discontinuation of treatment”, “persistent decrease in sex drive after discontinuation of treatment”, “persistent problems with ejaculation after discontinuation of treatment”, anxiety, “pain in the testicles”. Also “a decrease in the amount of semen released during sex” and the breast tissue line quoted above.
- Propecia 1 mg, summary of product characteristics, emc. Section 4.8: drug-related sexual side effects 3.8% on finasteride against 2.1% on placebo in the first 12 months, falling to 0.6% on finasteride over the following four years (no placebo figure given for that period). Post-marketing: persistence of sexual dysfunction after stopping.
- Proscar 5 mg film-coated tablets, patient information leaflet, emc. Section 4: erection problems, lower sex drive and ejaculation problems “that may continue after stopping the medication”. Section 2: for mood changes, “contact your doctor for further medical advice as soon as possible”.
- MHRA, Finasteride: reminder of the risk of psychiatric side effects and of sexual side effects (which may persist after discontinuation of treatment), Drug Safety Update, 29 April 2024. Patient card in all packs; ask about a history of depression or suicidal ideation; sexual dysfunction “has persisted even after treatment was stopped”; report “particularly if a side effect continued or started after treatment was stopped”. UK guidance.
- Healy D, Bahrick A, Bak M and colleagues. Diagnostic criteria for enduring sexual dysfunction after treatment with antidepressants, finasteride and isotretinoin. Int J Risk Saf Med 2022;33(1):65-76. Section 5: cognitive impairment, depression and suicidality are finasteride effects that can occur independently of any sexual difficulties. Proposed criteria from expert agreement.
- PFS Foundation, interview with Dr Michael Irwig, 28 August 2012, embedded as an extract from the start to 1:45. Used as background, not evidence for a figure.
- Moral Medicine, interview with Tim, 23 March 2026, embedded as an extract from 3:09 to 5:22. His story on our site: Tim.
Sources checked on 22 October 2026. AI-assisted writing and review, not clinical review.
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