Finasteride Side Effects: Sexual Side Effects, Mood, the MHRA Warning and Post-Finasteride Syndrome

Short answer: Finasteride 1mg, a daily tablet for male pattern hair loss, can cause sexual side effects and changes in mood, according to its UK product information (the Accord SmPC, sections 4.4 and 4.8, revised 28 September 2026). Uncommon side effects (fewer than 1 in 100 men): lower sex drive, low mood or depression, difficulty getting an erection, and changes in ejaculation, including less semen. In some men, sexual side effects have carried on after they stopped taking finasteride. Sexual side effects have also been linked to changes in mood, including thoughts of suicide. If you have any sexual side effects, ask our pharmacist or your GP for advice. If you notice changes in your mood, such as low mood, depression, anxiety or thoughts of suicide, stop taking finasteride and seek medical advice. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time. The MHRA, which regulates medicines in the UK, strengthened its warnings about these side effects on 11 May 2026. Your pack includes a patient card about possible mood changes and sexual side effects: read it and the leaflet before you start, and keep them both. Finasteride 1mg is a prescription-only medicine for men, supplied after a GPhC-registered pharmacist reviews your request.

This guide sets out what the product information for the finasteride 1mg we supply and the MHRA say, as of October 2026: how often each side effect happens, which need urgent help, the sexual side effects and those that carry on after stopping, post-finasteride syndrome, mood, the MHRA's warnings, testosterone, fertility, shedding, breast changes and PSA, who should not take it, and what to do if you get a side effect. It is about the 1mg tablet for male pattern hair loss, which is for men.

What are the side effects of finasteride?

The uncommon side effects of finasteride 1mg, affecting fewer than 1 in 100 men, are a lower sex drive, difficulty getting an erection, problems with ejaculation, including less semen, and depression; its UK product information lists no side effect as very common (more than 1 in 10) or common (up to 1 in 10). It lists others, including anxiety, thoughts of suicide, breast tenderness or enlargement and allergic reactions, with no known frequency, and in some men sexual side effects have carried on after stopping treatment.

Mood changes. If you notice changes in your mood, such as low mood, depression, anxiety or thoughts of suicide, stop taking finasteride and seek medical advice. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.

The table gives every side effect in section 4.8 of the product information, in plain words, grouped by its frequency bands.

Source: Accord Finasteride 1 mg film-coated tablets, Summary of Product Characteristics, section 4.8 (PL 20075/0085, revised 28 September 2026). It lists no side effect as rare (up to 1 in 1,000) or very rare either. The leaflet in your pack (section 4, last revised September 2026) lists the same side effects in everyday words: please read it before you start.

The NHS pages on finasteride, which cover both the 1mg tablet for hair loss and the 5mg tablet for an enlarged prostate, call erection problems, less interest in sex and ejaculation problems common, happening in more than 1 in 100 people, and say they usually improve after a while, but can sometimes carry on even after you stop taking finasteride. This guide follows the product information for the 1mg tablet we supply.

How to report a side effect

Tell our pharmacist or your GP about any side effect, so that a Yellow Card report can be sent to the MHRA. You can also report it yourself on the Yellow Card website or app, including a side effect that is not in the leaflet.

Which side effects of finasteride are serious?

Stop taking finasteride and contact a doctor straight away if you have thoughts of suicide, or signs of an allergic reaction such as swelling of your lips, face, tongue or throat, difficulty swallowing, hives or difficulty breathing: these are the urgent signs in its leaflet (section 4).

• If you notice changes in your mood, such as low mood, depression, anxiety or thoughts of suicide, stop taking finasteride and seek medical advice. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.
• Call 999 if your lips, mouth, throat or tongue suddenly swell, or you are struggling to breathe. These can be signs of a serious allergic reaction.
• Tell your doctor promptly about any changes in your breast tissue, such as lumps, pain or nipple discharge. The leaflet says these changes may be signs of a serious condition, such as breast cancer, and breast cancer has been reported in men taking finasteride (SmPC 4.4).

Can finasteride cause erectile dysfunction or a lower sex drive?

Yes, in some men: difficulty getting an erection, a lower sex drive and problems with ejaculation, including less semen, are uncommon side effects of finasteride 1mg, affecting fewer than 1 in 100 men (SmPC 4.8).

The product information adds that in some men sexual side effects may contribute to changes in mood, including thoughts of suicide, and that sexual side effects have also been reported without any change in mood (SmPC 4.4). If you notice changes in your mood, such as low mood, depression, anxiety or thoughts of suicide, stop taking finasteride and seek medical advice. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.

For a sexual side effect, the product information says a man should seek medical advice, and that stopping treatment should be considered. The MHRA also advises contacting your doctor for medical advice if you get a lower sex drive, difficulty getting an erection or problems with ejaculation (Drug Safety Update, 11 May 2026). Ask our pharmacist or your GP for advice about any sexual side effect.

If you take finasteride and are thinking about treatment for erection problems, tell the pharmacist. Finasteride is one of the cautions our prescription erectile dysfunction consultation asks about, and the pharmacist reviews it before anything is supplied; it does not stop an order on its own. Our pharmacy checklist for the erectile dysfunction tablets supplied without a prescription includes "Taking finasteride or dutasteride, for your prostate or for hair loss", and a man it applies to is asked to speak to his GP or use our full consultation instead. Erection problems have other causes too: see what is erectile dysfunction? and medicines that can cause erection problems.

Are finasteride side effects permanent?

Some can last: in some men, a lower sex drive, erection problems and ejaculation problems have carried on after they stopped taking finasteride, according to the UK product information, which gives no figure for how often this happens (SmPC 4.8).

The leaflet says some side effects are temporary while you carry on taking finasteride, or go when you stop (section 4), and the NHS says the sexual side effects usually improve after a while, but can sometimes carry on even after you stop. The MHRA reminded healthcare professionals in April 2024 that, in some cases, sexual problems have carried on even after men stopped taking finasteride.

If a side effect has not gone after you stop, see your GP. When you report it on Yellow Card, the MHRA asks you to say whether it carried on, or started, after you stopped treatment (Drug Safety Update, 29 April 2024).

What is post-finasteride syndrome?

Post-finasteride syndrome is a name some patients, patient groups and researchers use for symptoms reported as carrying on after stopping finasteride. The UK product information and the MHRA's safety warnings do not use the name: they describe sexual side effects, a lower sex drive, erection problems and ejaculation problems, that have carried on after treatment was stopped (Accord SmPC 4.8; MHRA Drug Safety Updates of April 2024 and 11 May 2026).

The MHRA's 2024 safety review report uses the name for a patient group, the Post Finasteride Syndrome Network, and in its review of published research. It records that members of the group asked the MHRA to classify post-finasteride syndrome as a recognised medical diagnosis, and says that is not within the MHRA's remit. What the MHRA does say is that finasteride is associated with depression, thoughts of suicide and sexual problems that may carry on after treatment is stopped (Drug Safety Update, 11 May 2026).

If you have symptoms that have not gone since you stopped finasteride, see your GP, who can assess them, and report them on Yellow Card. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.

Can finasteride cause depression or suicidal thoughts?

It can: the UK product information says low mood, depression and, less often, thoughts of suicide have been reported in men taking finasteride 1mg, and that if they happen, treatment should be stopped and medical advice sought (SmPC 4.4). It lists depression as uncommon, and anxiety and thoughts of suicide with no known frequency (SmPC 4.8).

The MHRA's advice is to stop finasteride 1mg immediately if you develop depression or suicidal thoughts and contact your doctor as soon as possible, and to call 999 straight away if you have seriously harmed yourself or feel at risk of serious harm. It also advises telling your doctor before you start finasteride if you have ever had depression or thoughts of suicide (Drug Safety Update, 11 May 2026). Our consultation asks about this before finasteride can be supplied, and the pharmacist reads your answer before deciding whether finasteride is suitable for you.

What did the MHRA change in 2024 and 2026?

In April 2024 the MHRA reminded healthcare professionals of the risk of psychiatric and sexual side effects with finasteride, including sexual side effects that may carry on after stopping, and on 11 May 2026 it strengthened the warnings for finasteride 1mg. The timeline shows each step.

The 2026 update followed a further detailed review of the evidence, including the outcome of a European review, with advice from the Commission on Human Medicines. It asks healthcare professionals to explain the risks when finasteride is supplied, to ask about any history of depression or suicidal thoughts, and to review patients regularly for psychiatric and sexual side effects (Drug Safety Update, 11 May 2026).

The MHRA has also said that finasteride 1mg is not available on the NHS and is often supplied online, which may increase the risk that its side effects are not explained well enough (press release, 29 April 2024). Our consultation sets out these side effects before every order, repeat orders included, and each repeat order asks about your mood and any breast changes: see the checks under "Is finasteride safe?" below.

Does finasteride lower testosterone?

The UK product information for finasteride 1mg does not say it lowers testosterone, or that it raises it: it describes finasteride as acting on the step that turns testosterone into DHT, and gives no figure for testosterone levels (SmPC 5.1).

Finasteride reduces the conversion of testosterone into DHT, the hormone behind male pattern hair loss. The enzyme it acts on, type 2 5-alpha reductase, is found in the hair follicles, and the balding scalp of men with male pattern hair loss has shrunken follicles and more DHT (SmPC 5.1). The leaflet says that in the scalp, finasteride lowers the level of DHT (section 1).

Neither the product information nor the MHRA's warnings explain the sexual side effects by a change in testosterone. Whatever the cause, the advice is the same: ask our pharmacist or your GP about any sexual side effect.

Does finasteride affect fertility?

Some men taking finasteride have reported poor sperm quality or infertility: the NHS says this is not common and that sperm usually returns to normal after stopping, and the product information says men planning to father a child should consider stopping treatment (SmPC 4.6).

The product information explains that long-term data on fertility are lacking, that men planning to father a child were left out of the original trials, and that in some of the reports the men had other risk factors that may have played a part. Semen quality returned to normal or improved after stopping in some reports. In a 48-week study of finasteride 1mg, no effect was seen on sperm count, how well sperm move or their shape, and longer-term data are not available (SmPC 5.1). If you are planning to father a child, talk to our pharmacist or your GP.

Finasteride passes into semen in small amounts. Use a condom if your partner is pregnant or could become pregnant. Women who could become pregnant should not handle crushed or broken finasteride tablets. Finasteride must not be taken by women: taken in pregnancy, it may cause abnormalities of a male baby's sex organs (SmPC 4.6). The tablets are coated, which prevents contact with the medicine during normal handling, as long as they are not broken or crushed (SmPC 4.2).

Does finasteride cause shedding?

Shedding is not listed as a side effect of finasteride 1mg: we have read its product information (SmPC, section 4.8) and its leaflet (section 4) in full, and neither mentions hair shedding.

Generally, three to six months of daily treatment are needed before hair loss stabilises. If your hair is coming out in patches or suddenly, or your scalp is red, sore or flaky, see your GP. These signs point to a cause other than male pattern hair loss. If you are worried that you are losing more hair than usual, speak to our pharmacist or your GP.

Minoxidil 5%, a licensed scalp spray for male pattern hair loss, has its own side effects, including a temporary shed when you start: they are in its leaflet, which you should read before you use it, and in our guide to minoxidil side effects. There is not enough evidence to recommend using finasteride and minoxidil together, so we do not supply the two together as a plan. If you already use minoxidil, tell our pharmacist during your consultation so they can advise you.

Can finasteride cause breast changes or affect a PSA test?

Yes to both: breast tenderness and enlargement are listed side effects of finasteride with no known frequency, breast cancer has been reported in men taking it, and it lowers PSA, a blood test used to check for prostate cancer (SmPC 4.4 and 4.8).

Tell your doctor promptly about any changes in your breast tissue, such as lumps, pain or nipple discharge. The leaflet says such changes may be signs of a serious condition, such as breast cancer.

Finasteride lowers PSA, a blood test used to check for prostate cancer. Tell your GP that you are taking finasteride. In trials in men aged 18 to 41, the average PSA level fell from 0.7 to 0.5 ng/ml over 12 months, and the product information tells doctors to consider doubling the PSA result of a man taking finasteride 1mg before they interpret it (SmPC 4.4). You can read whether we tell your GP.

Is finasteride safe?

Finasteride 1mg is a licensed medicine with the known side effects above, and it is not suitable for everyone. It is licensed for male pattern hair loss in men, and its product information says it must not be taken by women or children, by men already taking finasteride 5mg or another 5-alpha reductase inhibitor, or by anyone allergic to finasteride or its other ingredients (SmPC 4.1 and 4.3).

We also do not supply it if:

• you have a blockage affecting the flow of urine (obstructive uropathy)
• you have severe liver disease
• you have had a hair transplant
• you use antifungal, psoriasis or steroid creams on your scalp
• your hair loss has been linked to another medical condition, for example seborrhoeic dermatitis or cancer
• you have a rare inherited problem with galactose intolerance, total lactase deficiency or glucose-galactose malabsorption

Hair loss treatment through this service is for adults aged 18 and over. There is no upper age limit. Finasteride is licensed for male pattern hair loss in adult men only, so we are not able to supply it here. Hair loss in women needs a treatment licensed for women. Your GP or a pharmacist can advise.

How we check, before and during treatment:

• Before you can order, the consultation asks whether you have ever had depression, or thoughts of suicide or self harm, and shows a warning headed "MHRA warning: mood changes with finasteride", which says: "If you notice low mood, anxiety, or any thoughts of harming yourself, stop taking finasteride and seek medical advice straight away. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time."
• A GPhC-registered pharmacist reviews every request before finasteride is supplied. If they cannot approve it, we refund you in full.
• Repeat supplies need a review every 3 months, including a check for psychiatric symptoms.
• Each repeat order asks: "Since your last order, have you noticed any changes in your mood, such as low mood, depression, anxiety or thoughts of suicide?" A yes stops the order, with the advice to stop taking finasteride and seek medical advice. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.
• It also asks: "Since your last order, have you noticed any changes in your breast tissue, such as lumps, pain or nipple discharge?" From six months into a course, it asks how it is working, and your pharmacist reviews your answer.

You can see both licensed hair loss medicines on our hair loss page.

How can you reduce the side effects of finasteride?

The product information gives no way to prevent finasteride's side effects, so the practical steps are to take it as directed, tell us early about any side effect, and stop straight away if your mood changes.

• One 1mg tablet each day, at roughly the same time. Taking more does not help: its leaflet says finasteride will not work faster or better if you take it more than once a day (section 3).
• Swallow the tablet whole, without breaking or crushing it (SmPC 4.2).
• Ask our pharmacist or your GP about any sexual side effect. The product information says stopping treatment should be considered (SmPC 4.4).
• If you notice changes in your mood, such as low mood, depression, anxiety or thoughts of suicide, stop taking finasteride and seek medical advice. Call 999 or go to A and E if you feel unsafe, or call the Samaritans free on 116 123 at any time.
• Tell our pharmacist or your GP about any side effect, so that a Yellow Card report can be sent to the MHRA.

What happens when you stop taking finasteride?

If you stop taking it, the benefit begins to reverse by six months and is lost by 9 to 12 months. The leaflet says you are likely to lose the hair you have gained within the next 9 to 12 months.

The leaflet says some side effects go when treatment is stopped, although in some men sexual side effects have carried on afterwards (see above).

If it has not helped after a year, we recommend stopping it, and your GP can refer you to a dermatologist if you would like. How long finasteride takes to work is in our guide finasteride for hair loss: does it work?, and the two licensed medicines are compared in hair loss treatment in the UK. If your hairline is the worry, see receding hairline: early signs and causes.

For support, Alopecia UK (alopecia.org.uk) can help, and the British Association of Dermatologists has a patient leaflet.