Finasteride 5 mg (Proscar) side effects

Finasteride 5 mg (Proscar), taken for an enlarged prostate, can lower sex drive and cause erection and ejaculation problems. The UK leaflet warns that these may continue after stopping, a condition known as post-finasteride syndrome, or PFS.

The UK medicines regulator, the MHRA, calls men treated for an enlarged prostate “a typically older population more likely to experience sexual dysfunction”. The leaflet also warns of depression. The MHRA asks men to tell family and friends they’re taking it, as others may notice changes.

Tim was prescribed finasteride 5 mg in 2008 for a prostate problem. He was told he might need it for the rest of his life.

Play video: Tim on 17 years of finasteride 5 mg

He lost his sex drive and his erections, he says. After he started the tablets, his partner of 23 years decided they couldn’t carry on living “as brother and sister”. He kept taking them for about 17 years, until a warning card appeared in his pack.

What are the side effects of finasteride 5 mg?

The UK leaflet for Proscar names three sexual side effects: being unable to get an erection, wanting sex less, and problems with ejaculation, such as less semen.

These showed up early in a four-year trial of Proscar. In the first year, about 15 in 100 men had a sexual side effect the trial doctors linked to the tablets, against about 7 in 100 on a dummy pill. The trial recorded only what men raised themselves.

Sexual side effects in the first year, per 100 men

Finasteride 5 mg15

Dummy pill7

The leaflet also lists breast swelling or tenderness, pain in the testicles and blood in the semen. It asks men to “promptly report” to their doctor any change in breast tissue, such as lumps, pain, enlargement or nipple discharge, “as these may be signs of a serious condition, such as breast cancer”.

On mood, it says depressed mood, depression and, “less frequently, suicidal thoughts” have been reported. We cover these in the serious side effects of finasteride.

Can the side effects last after stopping?

For some men, yes. The Proscar leaflet says the sexual side effects “usually resolve after stopping”. It then lists erection, sex drive and ejaculation problems that “may continue after stopping the medication”.

The warning card in the pack agrees. Lower sex drive and erection problems have been reported, it says, “which in some cases continued after treatment was stopped”.

There’s no reliable figure for how often. In the four-year trial, some men left because of a sexual side effect. After stopping, it cleared up in about 5 in 10 of those on finasteride and about 4 in 10 of those on a dummy pill.

The published summary doesn’t say how long the men were followed, so it can’t show what happened to the rest. For some people it has lasted years after stopping. Nobody knows yet who will be affected, or whether it will ease.

Tim stopped when he saw the warning card. Almost a year later, he says, “nothing has changed”.

Tim’s 17 years on finasteride 5 mg

2008

One tablet a dayFor a prostate problem.

After starting

No sex drive, no erectionsHe didn’t link them to the tablets.

2025

A warning card in his packHe made the connection and stopped.

Almost a year on

“Nothing has changed”His words.

Could the drug still be in the body? See how long finasteride stays in your system.

Is Proscar the same as Propecia?

It’s the same drug at a different dose. Proscar is finasteride 5 mg, for an enlarged prostate. Propecia is 1 mg, for male hair loss.

The warning card goes in both packs. Our article on finasteride warnings shows how the UK warning grew. One instruction differs: if depression or suicidal thoughts develop, the MHRA says men on 1 mg should stop taking it and contact their doctor, while men on 5 mg should contact their doctor as soon as possible.

Rena Malik, a US urologist, says a man who gets through his first year without sexual side effects probably won’t develop them later. She also describes a survey of hair-loss patients whose sexual problems went on for years after stopping.

Play video: Rena Malik on finasteride and sexual side effects

Dutasteride, also taken for the prostate, is the same kind of medicine.

What can I do?

These medicines help many people. If you have side effects, that’s a decision for you and your prescriber.

If you develop low mood, depression or suicidal thoughts, the Proscar leaflet says to contact your doctor as soon as possible. If you’re struggling, the Samaritans are free to call on 116 123, day or night.

If sex has changed since you started, tell your GP and give your dates: “Finasteride 5 mg from March 2019. No erections since that summer.” Our page on post-finasteride syndrome explains what is known.

Many people say it took time to be taken seriously. Bring the card from your pack, or the leaflet line. You can report it without a doctor agreeing.

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.
• 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?

Can finasteride 5 mg cause depression? The leaflet lists depression as a side effect. A Canadian study followed older men who started finasteride or dutasteride for their prostate. It did not find a rise in suicide. It did find more self-harm in the first 18 months, and more depression, most clearly then. Records like these can’t prove the cause.

Does Proscar affect a PSA blood test? The leaflet says Proscar “can affect the results”, and to talk to your doctor or pharmacist if you’re having one. It also describes a seven-year trial. Fewer men taking finasteride developed prostate cancer than men taking nothing, but the number with “a high score in a tumour grading system” was higher “in some of those taking finasteride”. The effect of long-term use on tumours of this kind “is not known”, it says.

What should a partner know? You can report a side effect for him, with his permission, says the Yellow Card site. If his mood changes, the leaflet tells him to contact his doctor as soon as possible. If you’re pregnant or planning to be, it says not to touch crushed or broken tablets, and that he should use a condom.

It took a card in the pack, after about 17 years, for Tim to make the link. If you or your partner has taken finasteride for years, read the card together. If something changed and never came back, report it.

Sources

Every source below was checked on 11 October 2026.

1. Proscar 5 mg film-coated tablets, patient information leaflet (UK, electronic medicines compendium, emc 1008), Organon, last revised August 2024. The leaflet gives no frequencies.
   • Section 1: finasteride belongs to a group of medicines called 5-alpha reductase inhibitors. It is used for an enlarged prostate (benign prostatic hyperplasia).
   • Section 2: talk to your doctor or pharmacist if you are going to have a PSA blood test, “because Proscar can affect the results of this test”. Use a condom or other barrier method if your partner is pregnant or planning to become pregnant. Women who are pregnant or planning to become pregnant should not touch crushed or broken tablets.
   • Section 2, mood: “Mood alterations such as depressed mood, depression and, less frequently, suicidal thoughts have been reported in patients treated with Proscar. If you experience any of these symptoms contact your doctor for further medical advice as soon as possible.”
   • Section 4 opens with allergic reactions (stop and contact a doctor immediately). Then impotence, less desire for sex and ejaculation problems, which “may disappear after a while if you continue taking Proscar. If not, they usually resolve after stopping Proscar.”
   • Section 4, other side effects: “An inability to have an erection which may continue after stopping the medication”. “Decrease in sex drive that may continue after stopping the medication”. “Problems with ejaculation that may continue after stopping the medication”. Also breast swelling or tenderness, pain in the testicles, blood in semen, depression, anxiety and suicidal thoughts, and the line on breast changes quoted in the text.
   • Section 4, prostate cancer: Proscar “is not licensed to treat prostate cancer”. In a seven-year trial, the number of men who developed prostate cancer was lower on finasteride. The leaflet goes on: “The number of men who had a high score in a tumour grading system was higher in some of those taking finasteride compared to those taking nothing”. It ends: “The effect of long-term use of finasteride on tumours of this kind is not known”.
   • A generic leaflet we also opened, Finasteride 5 mg Tablets, Milpharm (revised July 2026), has the same lines on mood and on side effects that may continue after stopping.
2. Proscar 5 mg film-coated tablets, UK summary of product characteristics, text revised 20 December 2024. Section 4.1: licensed for benign prostatic hyperplasia. Section 4.4: mood alterations and depression; breast cancer in men. Section 4.8: decreased libido and impotence are common. Decreased libido, erectile dysfunction and ejaculation disorder that “may continue after discontinuation” are listed with frequency unknown, defined as “cannot be estimated from the available data”.
3. MHRA, Finasteride and dutasteride: updated safety warnings for psychiatric side effects and sexual dysfunction, Drug Safety Update volume 19, issue 10, 11 May 2026. The patient cards were “already introduced in 2024” and are supplied in the 1 mg and 5 mg packs. “Stop finasteride 1mg immediately if you develop depression or suicidal thoughts and contact your doctor as soon as possible”. “If you are prescribed finasteride 5mg or dutasteride and you develop depression or suicidal thoughts, contact your doctor as soon as possible”. Usage: “Prescribing data suggests more than 400,000 prescriptions per month are issued for finasteride 5mg and dutasteride containing medicines”, with a footnote to OpenPrescribing. “Dutasteride is also a 5-alpha-reductase-inhibitor.”
4. 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 volume 17, issue 9, 29 April 2024. Advice for patients: “it is very important to tell your friends and family that you are taking this medicine”, because “Others may notice changes”. The 5 mg dose (Proscar) is for benign prostatic hyperplasia in adults. The 1 mg dose (Propecia) is for male pattern hair loss.
5. MHRA, Finasteride: review of safety data and expert advice on management of risks, 29 April 2024. Annex 1 of the full report (PDF) has the card for finasteride 5 mg. It warns of depression and, in some cases, thoughts of suicide: “contact your doctor for further medical advice as soon as possible”. “Decreased sex drive and erectile dysfunction have also been reported (which in some cases continued after treatment was stopped)”. Section 5.1 calls men treated for an enlarged prostate “a typically older population more likely to experience sexual dysfunction as compared to patients treated for male pattern hair loss”.
6. Wessells H, Roy J, Bannow J and colleagues, for the PLESS Study Group. Incidence and severity of sexual adverse experiences in finasteride and placebo-treated men with benign prostatic hyperplasia. Urology 2003;61(3):579-84. The Proscar Long-term Efficacy and Safety Study: 3,040 men aged 45 to 78, four years, finasteride 5 mg against placebo. Men filled in a questionnaire on their sexual history at screening. During treatment, sexual side effects were “spontaneously self-reported”. Year one: 15% on finasteride and 7% on placebo had sexual side effects the investigator considered drug related. Years two to four: 7% in each group. 4% on finasteride and 2% on placebo left the study because of one. Among men who left with one, it resolved after stopping in 50% (finasteride) and 41% (placebo). Read from the published abstract, which gives no length of follow-up after stopping.
7. Welk B, McArthur E, Ordon M and colleagues. Association of suicidality and depression with 5α-reductase inhibitors. JAMA Intern Med 2017;177(5):683-91. Health records of 93,197 men aged 66 or over in Ontario who started finasteride or dutasteride for an enlarged prostate, matched with the same number who did not. No significant increase in suicide. Self-harm was raised in the first 18 months. Depression was raised in the first 18 months and, less so, afterwards. Absolute increases: 17 per 100,000 patient-years for self-harm and 237 per 100,000 patient-years for depression. An observational study: association, not proof of cause.
8. MHRA, Yellow Card: how to report: “You can report for yourself or for someone else, with their permission.”
9. Moral Medicine, He Took Finasteride for 17 Years… Then His Doctor Refused to Help, interview with Tim, 23 March 2026 (the title is the channel’s). Our page plays an extract, 3:07 to 5:21; the views are his own. Quotes are from YouTube’s automatic captions. Outside the extract: “as brother and sister” (2:16), the interviewer dates the end of the relationship to 2009 and Tim agrees (2:35), told he might have to take it for the rest of his life (2:52). In the extract: no libido and no erections (3:13), finasteride from 2008 until 2025 at 5 mg a day (4:02), the warning card and stopping (4:45), “nothing has changed” (5:00), off it almost a year (5:13). His story on our site: Tim’s story: nearly 17 years on finasteride.
10. Rena Malik, M.D., Tamsulosin and Finasteride side effects: are they reversible?, 17 June 2022 (the title is shortened from the channel’s). Our page plays an extract, 0:37 to 3:24, the part about finasteride; the views are her own. Paraphrased from YouTube’s automatic captions: the first-year point at 2:10, the survey of men with lasting problems from 2:20.
11. MedDRA term and code: Post 5-alpha-reductase inhibitor syndrome, 10082430.