Hair loss treatment risks: what can last?

Worried a hair loss treatment could leave lasting problems? The medicines with the biggest warnings are finasteride and dutasteride, which lower a hormone called DHT.

Their UK leaflets say sexual problems may continue after stopping. When problems carry on, it’s called post-finasteride syndrome (PFS).

Most online clinics sell these tablets as a simple fix for a receding hairline. The UK Propecia leaflet lists “persistent difficulty having an erection after discontinuation of treatment”, and many men only find that line later.

So which treatments carry the warning, and what should you know before you start?

Which hair loss treatments carry the warning?

The warning about lasting problems is on medicines that block DHT. Finasteride tablets (Propecia 1 mg, and Proscar 5 mg for the prostate) carry it. So does dutasteride, which works the same way and is sometimes prescribed off-label for hair.

Finasteride sprays and gels lower DHT too, though less. In 2025 the US regulator, the FDA, warned about compounded sprays after reports of side effects that went on after people stopped. Our article on topical finasteride covers it.

Minoxidil works differently. Its UK foam label lists no sexual side effects, and it isn’t linked to PFS. Our comparison of the three sets out what each leaflet says.

Supplements and “hair growth pills” sold online are a separate category. If a product says it blocks DHT, ask what’s in it.

What side effects are people warned about?

The leaflets mainly warn about sex and mood. The UK Propecia leaflet lists lower sex drive, erection problems, less semen and pain in the testicles. It also lists problems with sex drive, erections and ejaculation that persist “after discontinuation of treatment”.

It lists depression and suicidal thoughts too, and says to stop taking Propecia and contact your doctor if they happen. If you’re having those thoughts, call the Samaritans on 116 123, free, at any hour.

Men with PFS describe much more than the leaflet lists. They talk about brain fog and memory problems, poor sleep, feeling emotionally flat, numbness and muscle twitching. Our list of PFS symptoms goes through them in their words.

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.

Play video: Dr Michael Irwig on lasting side effects of finasteride (extract)

How common are they? While men are taking finasteride, sexual side effects 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.

Lasting problems are a separate question. Nobody has measured how often they happen. Reports to a regulator can’t give a rate, and many side effects are never reported.

So a low number of reports isn’t proof of safety. That’s why each report counts.

Can the side effects last after stopping?

For some men they do. The MHRA, the UK medicines regulator, says sexual problems have “persisted even after treatment was stopped”. The Avodart leaflet says the same of dutasteride: “this may continue after you stop taking Avodart”.

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.

PFS is more than sexual problems. Criteria proposed by doctors and researchers in 2022 also describe cognitive problems, depression and suicidal thoughts, which can happen with or without sexual changes.

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.

Play video: Tim on 17 years of finasteride 5 mg (Moral Medicine, extract)

What can I do?

These medicines help many men keep their hair. If you’re thinking of starting, read the leaflet and the card first. 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.

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?

Are hair growth pills bought online safer? A tablet from an online clinic is the same medicine. A quick online form may not cover the leaflet’s warnings, so read the leaflet and the card either way. Our article on buying from Hims, Keeps and Boots looks at this.

Can a few tablets cause problems? Some men say their symptoms began after a short course. Nobody has studied how dose or length of use affects the risk. Our article on PFS after a few pills covers what people describe.

Is PFS real? The UK leaflet and regulator both describe sexual problems that persist after stopping. The name PFS isn’t in the leaflet, but it is now a recognised term for reporting. See is PFS real?

Tim found the warning in his box after 17 years. If you’re on a hair loss tablet and something has changed, write down the dates and report it. Our PFS page is a good place to start.

Sources

1. Propecia 1 mg film-coated tablets, patient information leaflet, electronic medicines compendium (emc), last revised May 2026. Section 2: depression and suicidal thoughts; “stop taking Propecia and contact your doctor for further medical advice”. 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”; also anxiety, pain in the testicles and less semen.
2. 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.
3. 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; side effects “are not well known by prescribers and patients”; sexual dysfunction “has persisted even after treatment was stopped”; report “particularly if a side effect continued or started after treatment was stopped”. UK guidance.
4. Avodart 0.5 mg soft capsules, patient information leaflet, emc: sexual side effects “may continue after you stop taking Avodart”. Licensed in the UK for the prostate, not for hair loss.
5. Regaine for Men Extra Strength Scalp Foam 5%, summary of product characteristics, emc. Section 4.8 lists no sexual side effects.
6. US Food and Drug Administration, alert on compounded topical finasteride products, April 2025. Reported adverse events that “continued to persist after product discontinuation”. US guidance.
7. 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.
8. 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.
9. Moral Medicine, interview with Tim, 23 March 2026, embedded as an extract from 3:09 to 5:22.

Sources checked on 22 October 2026. AI-assisted writing and review, not clinical review.