Finasteride Sexual Side Effects: How Common Are They, And Do They Last?
Last reviewed on 30 July 2026. We review our treatment guides every six months to keep them accurate.
Key points
Finasteride can cause sexual side effects: a lower sex drive, erectile dysfunction, and problems with ejaculation. These are the most talked-about risks of the drug.
They are uncommon. In the manufacturer's trials, any sexual side effect affected about 3.8 per cent of men on finasteride in the first year, against 2.1 per cent on a dummy pill, and the rate fell further with continued use.
For most men who do get them, they settle, either while continuing the drug or after stopping it. But in a minority, sexual dysfunction has been reported to persist after stopping, which is the most important and least understood part of the picture.
The UK regulator, the MHRA, strengthened its warnings in 2024 and again in 2026, introduced a patient alert card in every pack, and links finasteride with depression and suicidal thoughts as well as sexual dysfunction.
The official advice is clear on one point: stop finasteride 1mg and contact your doctor straight away if you develop depression or suicidal thoughts. For sexual side effects, speak to your prescriber rather than stopping or changing anything on your own.
This page is general information. It is not medical advice and not a reason to start or stop a prescribed medicine without talking to your doctor.
Finasteride is one of the few treatments proven to slow male pattern hair loss, and for many men it works well and without trouble. But its sexual side effects are the single biggest reason men hesitate to take it, or worry once they have started, and the subject is surrounded by strong opinions online that are not always accurate in either direction.
This guide sets out what the sexual side effects actually are, how common they are according to the manufacturer's own trial data, whether they go away, and what UK regulators now advise, so you can weigh it up with your prescriber on the basis of evidence rather than forum anecdote.
For the current UK safety position, the MHRA Drug Safety Update on finasteride is the authoritative source.
What are the sexual side effects of finasteride?
Finasteride works by lowering levels of dihydrotestosterone (DHT), the hormone that both drives male pattern hair loss and plays a part in normal sexual function. Reducing it is how the drug protects hair follicles, and it is also why a small number of men notice effects on sexual function.
The recognised sexual side effects, as listed in the Propecia patient and product information, are a decreased sex drive (libido), erectile dysfunction, and ejaculation disorders, which mainly means a reduced volume of ejaculate. The MHRA groups these together as "sexual dysfunction" and, importantly, notes that they have been reported both alongside low mood and entirely on their own.
How common are finasteride sexual side effects?
Uncommon, and it is worth being precise about the numbers rather than relying on impressions, because the reality is less frightening than the online discussion often suggests, while still being real.
In the manufacturer's clinical trials, reported in the Propecia product information, the drug-related sexual side effects during the first year of treatment affected about 3.8 per cent of men taking finasteride, compared with 2.1 per cent of men taking a placebo. Broken down, the individual figures over the first year were a decreased sex drive in 1.8 per cent of men on finasteride against 1.3 per cent on placebo, and erectile dysfunction in 1.3 per cent against 0.7 per cent. So the effect is real but modest, and a proportion of the men reporting it in trials were reacting to the act of taking a pill rather than to the drug, which is why the placebo figures are not zero.
The trial data also show the rate falls with time rather than building up. By the fifth year of treatment, the proportion of men reporting these effects had dropped below 0.3 per cent, and roughly 1 per cent of men in each group, finasteride and placebo alike, stopped treatment because of a sexual side effect in the first year.
The honest summary is that the large majority of men who take finasteride do not experience sexual side effects, and of those who do, most find they ease over time or on stopping. That is the reassuring part. The next section is the part that requires more care.
Do finasteride sexual side effects go away, and what is post-finasteride syndrome?
For most men, yes. Where sexual side effects occur, they commonly resolve either while continuing the medication or after stopping it. But the reason this topic is taken so seriously is a minority in whom they do not.
The Propecia product information records that persistence of sexual dysfunction, meaning decreased libido, erectile dysfunction and ejaculation disorder continuing after the drug is stopped, has been reported in post-marketing use. The cluster of persistent symptoms that some men describe after stopping finasteride is often referred to online as "post-finasteride syndrome". It is a genuinely reported phenomenon that regulators take seriously, but it is not fully understood: how often it truly occurs, why it affects some men and not others, and its exact mechanism are all still uncertain, partly because reports of this kind cannot easily separate the drug's effect from other causes of the same symptoms.
What can be said honestly is this: persistent sexual dysfunction after finasteride is uncommon, but it is real enough that the UK regulator has acted on it, and it is the single most important thing to understand before starting. It is a reason to make the decision carefully and with a prescriber, not a reason to panic if you are already taking the drug without problems.
What do UK regulators say about finasteride?
The MHRA, which regulates medicines in the UK, has strengthened its warnings on finasteride twice in recent years, and the detail matters because it also concerns mood, not only sexual function.
In April 2024, following a safety review and concern that these risks were not well known, the MHRA introduced a patient alert card into every pack of finasteride, highlighting the risk of sexual side effects and of psychiatric side effects including depression and suicidal thoughts, and noting the potential for sexual dysfunction to persist after treatment is stopped. At that point the MHRA had received 426 UK reports of finasteride and sexual dysfunction, and 281 reports of depression or suicidal and self-injurious behaviour, dating back to the 1990s.
In May 2026 the MHRA strengthened the warnings further, clarifying in the product information that sexual dysfunction may contribute to mood disorders, and that it has been reported both with and without mood changes. The link between the sexual and the psychiatric effects is part of why this is treated as more than a purely physical side effect.
The practical instructions that come out of this are specific, and worth stating exactly:
If you develop depression or suicidal thoughts while taking finasteride 1mg for hair loss, stop taking it immediately and contact your doctor as soon as possible. This is the MHRA's direct advice and it is not something to wait on.
Read and keep the patient alert card and the leaflet that come in the pack, and tell your doctor before starting if you have any history of depression or suicidal thoughts.
Suspected side effects can be reported to the MHRA through its Yellow Card scheme, which is how this evidence is gathered.
What should you do if you get sexual side effects?
First, do not rely on this page or on online forums to make the decision, and do not quietly stop or switch a prescribed medicine without speaking to the person who prescribed it. Talk to your prescriber or GP, who can weigh your particular situation.
If the problem is a sexual side effect alone, the options a doctor might discuss include continuing to see whether it settles, since many do, lowering the dose, taking a break from the drug, or stopping it. Because finasteride only works while it is taken, stopping means hair loss will gradually resume, so it is a genuine trade-off to talk through rather than an obvious answer. If low mood, depression or suicidal thoughts are present at all, the advice is different and firmer: stop the 1mg tablet and seek medical help promptly, as above.
One option some men ask about is topical finasteride, applied to the scalp rather than taken as a tablet, on the theory that less reaches the bloodstream. Our guide on topical versus oral finasteride covers this honestly: topical finasteride does reduce blood levels of the drug, but it is still absorbed and is not a guaranteed way to avoid sexual side effects, and in the UK it is not a licensed medicine. It is a conversation for your prescriber, not a simple fix.
Weighing it up
Finasteride is a genuinely effective hair-loss treatment with a side-effect profile that, for most men, is mild or absent. The sexual side effects are uncommon, usually reversible, and modest in the trial data. Set against that is a real but poorly quantified risk that in a minority they persist after stopping, and a regulator that has twice strengthened its warnings and now includes an alert card in every pack. Neither the online view that finasteride routinely ruins men, nor the older view that its side effects are trivial and always reversible, matches the evidence. The truth sits in between, and it is personal.
The sensible approach is an informed conversation with a prescriber who will tell you about the risks, check your history, review how you get on, and treat any mood symptoms as a reason to stop and seek help. Hair loss is not a medical emergency, and there is no wrong choice in deciding the risk is or is not worth it for you. What matters is that the decision is made with the facts. Related reading includes our guides on finasteride for hair loss generally, dutasteride, which carries similar warnings, and finasteride and trying for a baby.
Frequently asked questions
How common are sexual side effects with finasteride?
Uncommon. In the manufacturer's trials, any sexual side effect affected about 3.8 per cent of men on finasteride in the first year, against 2.1 per cent on a placebo, with erectile dysfunction specifically in 1.3 per cent against 0.7 per cent. The rate fell below 0.3 per cent by the fifth year. Most men who take finasteride do not experience sexual side effects.
Do finasteride sexual side effects go away when you stop?
For most men they resolve, either while continuing the drug or after stopping it. However, the product information records that in some men, sexual dysfunction has persisted after stopping. This persistent form is uncommon but is real enough that the UK regulator has strengthened its warnings, which is why the decision to take finasteride is worth making carefully with a prescriber.
What is post-finasteride syndrome?
It is the term used, mainly online, for a cluster of symptoms, often sexual but sometimes including low mood, that some men report as persisting after they stop finasteride. It is a genuinely reported phenomenon that regulators take seriously, but how often it occurs and why is still not well understood, and reports cannot easily separate the drug from other causes of the same symptoms. It is uncommon, but it is the main reason to consider finasteride carefully before starting.
Should I stop finasteride if I get side effects?
Do not stop or change a prescribed medicine without talking to your prescriber, with one exception: the MHRA advises that if you develop depression or suicidal thoughts while taking finasteride 1mg, you should stop immediately and contact your doctor as soon as possible. For sexual side effects on their own, speak to your prescriber about whether to wait, adjust the dose or stop, since stopping means hair loss will gradually return.
Does topical finasteride avoid sexual side effects?
Not reliably. Topical finasteride, applied to the scalp, does lower the amount of the drug reaching the bloodstream compared with a tablet, but it is still absorbed and sexual side effects can still occur. It is also not a licensed medicine in the UK. It is worth discussing with a prescriber rather than treating as a guaranteed way to avoid side effects.
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