Post-finasteride syndrome (PFS)

Post-finasteride syndrome (PFS) is a multisystem condition caused by finasteride and related drugs. Symptoms can begin during treatment or only after stopping, and continue after the drug has left the body.

Half of a dose leaves the blood within 5 to 6 hours, yet PFS can last for years. Nobody yet knows why.

PFS is one of three related conditions, with PSSD (after SSRI and SNRI antidepressants) and PAS (after isotretinoin). The 2022 criteria cover all three.

The 2022 diagnostic criteria

There is no blood test or scan for PFS. In 2022, 37 doctors and researchers from ten countries agreed diagnostic criteria for it.

• Required: you took finasteride or a related drug, such as dutasteride.
• Required: sexual problems continued after you stopped.
• Supporting: low desire, erectile dysfunction or less genital and orgasm feeling, lasting 3 months or more.
• Ruled out: the same problems before the drug, or another illness, medicine or drug use that explains them. The criteria also ask for no earlier isotretinoin or SSRI-type antidepressant.

Problems that clear after stopping are not PFS. A mental health diagnosis does not rule it out. The criteria are an expert consensus, not official guidance, built from cases reported to RxISK.org, a drug safety website linked to three of the authors.

Names, codes and drugs

The criteria require sexual symptoms. Depression, cognitive problems and suicidal thoughts can come with them or appear on their own, the criteria say.

The sexual symptoms come from the 2022 criteria, and the UK product information lists depression, anxiety and suicidal thoughts. The rest come mainly from patient reports, collected in Orphanet’s entry and a survey of 131 men with symptoms.

Symptoms can start while you take the drug. For some people they first appear, or get worse, after stopping. More in what happens when you stop taking finasteride.

Most published cases are young men who took finasteride 1 mg for hair loss. Beyond that, little is known about who is at risk.

• Age. The 1 mg dose is licensed for men aged 18 to 41. In reports to the FDA (the US regulator), men with lasting problems after Propecia were younger than those after Proscar, the prostate dose.
• Dose. Lasting problems have been reported after both 1 mg and 5 mg. UK reports come more often from 1 mg, though 5 mg is prescribed more. The MHRA, the UK regulator, says this “does not necessarily mean a different level of risk”.
• How long. In a PFS Network survey of its own members, just over half of 427 respondents had used finasteride for 200 days or less. Yet in one US records study, young men on it for over 205 days had more lasting erectile dysfunction than shorter users.
• Sex. Finasteride is not licensed for women in the UK. In the MHRA’s 2023 search, all UK reports of sexual side effects that gave a sex came from men. We found no study of lasting side effects in women.
• Mental health history. Some studies found side effects more likely after a personal or family history of mental illness, but the MHRA notes many were small and relied on memory.

Nobody knows why some people are affected and others are not, and no test can predict who will be.

Nobody knows how common PFS is. Regulators hold hundreds of reports, but no one has measured a rate.

While people take finasteride, the UK label rates lower sex drive and depression as “uncommon” (1 in 1,000 to 1 in 100 people). For problems after stopping, it gives no figure.

What is reported

By April 2024 the MHRA had 426 Yellow Card reports (the UK reporting scheme) of sexual problems with finasteride. In almost half, the outcome was recorded as “not recovered” or “not resolved”.

Why there is no rate

A rate needs two numbers: how many people have PFS, and how many took finasteride. Neither is known; the MHRA calls this a “lack of denominator”. Finasteride 1 mg is not prescribed on the NHS, so “accurate prescription numbers are not available”.

Trials “do not routinely include follow-up” to check that sexual side effects clear, the criteria’s authors write. In 2012 the FDA knew of no controlled study “to determine their cause or duration”.

Studies of frequency

• The trials. During treatment, 3.8% of men on finasteride reported a sexual side effect, against 2.1% on placebo (a dummy pill). From these trials, the FDA says “only a small percentage of men” are affected.
• Medical records. A 2017 US study looked at 11,909 men given finasteride or dutasteride. Of these, 167 (1.4%) had erectile dysfunction that lasted at least 90 days after stopping. Among 4,284 men aged 16 to 42 on the hair-loss dose, it was 34 (0.8%). One health system, erectile dysfunction only, no proof of cause: not a rate for PFS.

The MHRA adds that media attention and the “nocebo” effect (symptoms caused by expecting harm) may add to reports. A study with a comparison group, following people after they stop, would answer the question.

Regulators in the UK and the US warn that finasteride’s sexual side effects can continue after stopping. None has recognised PFS as a condition. When patients asked, the MHRA said that is “not within the MHRA’s remit”.

How finasteride 1 mg is supplied in the UK

In the UK, finasteride 1 mg is not prescribed on the NHS. It comes from private clinics or, “more often”, from online pharmacies. Regulating pharmacies “is not within the remit of the MHRA”; the General Pharmaceutical Council sets their standards.

Some online pharmacies screen and monitor patients thoroughly, the MHRA found, and “others do not”.

Is finasteride safe? What regulators conclude

In 2025 the EMA (the EU medicines agency) concluded that the benefits of finasteride and dutasteride “continue to outweigh their risks for all approved uses”. No regulator can yet say how often the lasting harm happens.

By 31 May 2025 the MHRA had 170 reports of suicidal thoughts and related terms with finasteride, and 19 reports of death by suicide. These are reports, not a rate. The MHRA adds that a report “does not necessarily mean that the medicine has caused the reaction”.

If this is close to home, Samaritans are on 116 123 in the UK, free, at any hour. In the US, call or text 988.

More in finasteride warnings from the MHRA, EMA and FDA and finasteride and suicidal thoughts.

Research on PFS is small and comes mostly from a few groups. It has found differences in men with PFS, but it is “not clear whether these were present before treatment”.

Most of these studies measured small groups of men with PFS once, after the drug. Following people from before they start would show which changes came first.

There is no test for PFS. A doctor diagnoses it from your history, using the 2022 criteria: what you took, when, and what changed.

Your doctor may not have come across it. The criteria’s authors write that these conditions are “little known and poorly understood by healthcare professionals”.

What to bring to your doctor

• The patient card from the pack, if you have one: it says these effects may continue.
• A printed copy of the 2022 criteria, which are free to read.
• Your dose, and roughly when you started and stopped.
• What changed, and when. Say whether it started or continued after stopping.
• Any change in mood, even if it seems unrelated.
• Other medicines, past and present, especially antidepressants or isotretinoin.

Ruling out other causes

The criteria require that no other illness, medicine or drug explains your symptoms. So a doctor may check for other causes first. That is part of a proper diagnosis, not a sign of disbelief.

Normal blood tests do not settle it either way. Borderline hormone levels may be “a consequence of the conditions rather than a cause”, the criteria’s authors write.

More in how to approach your doctor about PFS and the diagnostic criteria for PFS.

There is no approved treatment for PFS. In September 2026 we found no treatment trial for it registered on ClinicalTrials.gov.

What research is testing

The Milano Project at the University of Milan, led by Professor Roberto Melcangi, which SIDEfxHUB raises money for, is working towards a possible treatment. In rats, allopregnanolone reduced several changes seen after finasteride was stopped. It has not been tested in people.

Is PFS permanent?

It can be. PFS “can remain for months, years or indefinitely” after the drug is stopped, the criteria’s authors write. How many people recover fully “has never been properly investigated”.

A 2012 follow-up study reassessed 54 men 9 to 16 months later, and 96% still had symptoms. But they were chosen because their symptoms had already lasted, so this cannot tell you your own chances.

So nobody can tell you whether your own PFS will pass. More in is full recovery from PFS possible?

How to judge a treatment offer

You may come across treatments offered online or in private clinics. We do not recommend any. These questions help you and your doctor weigh an offer:

• Has it been tested in people with PFS, with a comparison group? Or only in case reports, patient stories or animals?
• What are its own side effects, and what happens when you stop it?
• What does it cost, and does the person recommending it also sell it?
• Will your own doctor know you are taking it?

SIDEfxHUB is a UK patient charity (registered charity 1203385) for people living with PFS, PSSD and PAS. We fund research, push for these conditions to be recognised, and support patients.

• The registry. Our registry follows people over months and years. Its members chose to join, so it cannot say how common PFS is. It can show how symptoms change over time, which a one-off report cannot.
• Research. We raise money for the Milano Project at the University of Milan, which studies what finasteride and SSRIs change in the body. Its two studies published so far were done in rats.

Every source below was checked on 26 September 2026.