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Home / Men's Health / Finasteride side effects: All you need to know
Finasteride 1mg: a prescription-only daily tablet licensed in the UK for male pattern hair loss.
Short answer

Most men take finasteride 1mg and notice little to no side effects.

Sexual side effects are listed as uncommon in frequency, meaning fewer than 1 in 100 men experience them, and in the trial, they were barely more common than on a placebo tablet.

The exception worth taking seriously is mood changes, where UK and European regulators strengthened their warnings between 2024 and 2026.

What's in this article

Before you read on

Finasteride is a prescription-only tablet, taken once a day, that slows male pattern hair loss and helps with hair regrowth. The medicine has been licensed for this use in the UK since the late 1990s.

But, like every prescription medicine, Finasteride comes with its own side effects.

If you have been ruminating on your decision to take Finasteride due to the fear of experiencing side effects, that is normal.

Most men do.

The difficulty is that researching about finasteride’s side effects often leave people more worried than when they started.

This guide lays out a clear list of side effects you might experience when you start finasteride for hair loss.

Before you begin: A little bit about OnlineClinic

OnlineClinic has been operating since 2011 and has treated more than 2.1 million patients.

The pharmacy is registered with the General Pharmaceutical Council (GPhC), our prescribers are registered with the General Medical Council (GMC), and the service is regulated by the Care Quality Commission (CQC).

As of August 2026, on Trustpilot, the service rating is 4.6 out of 5 based on 6,898 reviews.

Why the side effect statistics can be misleading

Two things distort what you find online.

The first is who bothers to post.

Men who have no side effects have no reason to write about them.

Men who do have every reason.

So the sheer volume of what you read tells you almost nothing about how likely any of it is.

The second is dose.

Finasteride 1mg is the licensed treatment for male pattern hair loss.

Finasteride 5mg treats an enlarged prostate, and is taken mostly by men decades older, many of whom already have some erectile difficulty.

Alarming statistics usually come from that second group, then get quoted as though they apply to a man in his thirties taking a fifth of the dose for his hair.

How does finasteride work

Finasteride works by lowering DHT, the hormone that shrinks genetically sensitive hair follicles.

It barely touches testosterone.

In a 1999 study, the 1mg dose cut scalp DHT by 64% and DHT in the blood by 71%, which is why most men keep normal libido, energy, and muscle.

What do finasteride’s clinical trials show

In the trial behind UK licensing, expert review of standardised photographs found improvement in 48% of men at one year and 66% at two years, against 7% on placebo.

At two years, 83% of men on finasteride had no further loss.

Nobody can promise you a particular result, and it only works while you take it: the product information notes the benefit reverses over about 6 months if you stop, and returns to baseline within 9 to 12 months.

Finasteride is prescription-only. It is not licensed for women and must not be taken by anyone under 18.

Finasteride side effects: Myths vs evidence

What you'll read online What the evidence shows
Nearly everyone gets side effects The gap over placebo was under 2% for every sexual side effect measured
Side effects are always permanent Most side effects resolve over time. A minority of users report persistent side effects, which is real but uncommon
It causes depression in everyone Depression showed no difference from placebo in the phase III trials. The signal is concentrated in younger men, which is why mood is monitored
It shrinks your penis No credible evidence
It causes permanent infertility Effects on sperm at 1mg are uncommon and the evidence indicates they reverse
Topical or low-dose versions are risk-free Lower exposure plausibly means lower risk, not zero.
Stopping puts everything back to normal Side effects usually settle, but the hair benefit also reverses within about a year

What are finasteride’s side effects

Like most prescription medicines, finasteride also comes with its own set of side effects.

Three sexual side effects were measured directly against placebo in the licensing trials.

All three are classed as uncommon in UK product information, which means they affect between 1 in 1,000 and 1 in 100 men.

Side effect Finasteride 1mg Placebo
Reduced libido 1.8% 1.3%
Erectile dysfunction 1.3% 0.7%
Reduced ejaculate volume 0.8% 0.4%

Figures are from the UK Summary of Product Characteristics for finasteride 1mg, linked at the end.

Drug-related sexual side effects in the first year affected 3.8% of men on finasteride and 2.1% on placebo.

Rates then fall the longer men stay on it, dropping below 0.3% by year five.

Roughly 1% of men in each group stopped because of sexual side effects, which is why the overall dropout rate was slightly lower on finasteride (1.7%) than placebo (2.1%).

Depression is also listed as an uncommon side effect. In the phase III trials, it was no more common on finasteride than on placebo, and it was added to the product information later, based on the reports from real-world use.

Side effects with no established frequency

Some side effects were only identified once the medicine was in widespread use.

Those reports arrive voluntarily rather than from a controlled trial, so there is no way to calculate how often they occur.

The UK product information lists them as "not known" in frequency, which is a gap in the data rather than a sign they are trivial. Some of these side effects are as follows:

  • Anxiety
  • Suicidal thoughts (covered in the next section)
  • Breast tenderness or enlargement
  • Testicular pain
  • Rash, itching, hives, or swelling
  • Blood in the semen

Any breast lump or tenderness should always be reported, because male breast cancer, though very rare, has been recorded in men taking finasteride.

Start your free finasteride consultation

Finasteride is prescription-only, and a GMC-registered prescriber will go through all of this with you before anything is issued.

Mood changes on finasteride: What regulators decided

The regulators in the UK and Europe have recently updated their guidelines on finasteride. Here’s what has happened in the last two years.

What changed recently

  1. April 2024. The MHRA strengthened warnings on psychiatric and sexual side effects, and put a patient alert card in UK finasteride packs.
  2. May to August 2025. After a European review, suicidal ideation was confirmed as a side effect of finasteride tablets. The frequency was recorded as unknown, and the benefits were judged to still outweigh the risks.
  3. May 2026. The MHRA added that sexual dysfunction may contribute to mood problems, and that mood problems have also been reported without any sexual side effects.

The European regulator treats the link with suicidal thoughts as established enough to list as a side effect in its own right, while stating plainly that nobody can say how often it happens.

So the practical position is not complicated:

  • If you have ever had depression, anxiety, or suicidal thoughts, tell your prescriber about it before you start.
  • If your mood drops on finasteride, stop the tablets and contact your prescriber or GP.
  • If you have thoughts of harming yourself, treat it as urgent and get help the same day. Call 999 if you feel at immediate risk.

Post-finasteride syndrome: What is it and is it real

Post-finasteride syndrome, or PFS, describes symptoms some men report after stopping: Persistent erectile difficulty, low libido, low mood, fatigue, and difficulty concentrating.

The evidence comes mostly from case series and self-selected online registries. The research can tell us that some men experience this, but not how often it happens.

Do specialists think PFS is real?

Mostly, they think the evidence isn't yet strong enough to say anything either way.

The prevailing view in that survey was that the cause is psychological rather than hormonal.

That is one national group's opinion rather than a settled international position.

It is also not a comfortable thing to read if you are the one with the symptoms, and being told a problem is psychological does not make it any less real to live with.

Regulators have stopped short of either endorsing PFS or dismissing it.

A fair reading: Persistent symptoms are reported by a minority and should not be waved away, but a proven, irreversible syndrome caused by the drug is not established.

There is no test for it and no proven treatment, which is exactly why stopping early beats pushing through.

If side effects do happen

For most men, the side effects fade away over time.

If you’re suffering from erectile dysfunction, it’s best to consult your prescriber about it. You can start your free online erectile dysfunction consultation at OnlineClinic.

Quick tip

If libido, erections, or mood changes occur in the first few weeks, do not give it months to settle on its own. Speak to a prescriber.

Who should not take finasteride

Finasteride 1mg is licensed for adult men only. It is not for:

  • Hair loss not caused by male pattern baldness
  • Women, including for female pattern hair loss
  • Anyone under 18
  • Anyone with a known allergy to finasteride

Tell your prescriber if you have:

  • Any history of depression, low mood or suicidal thoughts
  • Liver problems, which affect how the drug is cleared
  • A planned or recent PSA test, or any prostate symptoms
  • A partner who is pregnant or trying to conceive, so you can discuss handling

Please note: Pregnant women must not touch broken or crushed Finasteride tablets. Finasteride can cause problems for an unborn baby if it is absorbed into the skin of a pregnant woman.

Also note: The pivotal trials enrolled men aged 18 to 41, which is why the labelling quotes its PSA figures for that group.

What does finasteride cost at OnlineClinic

At OnlineClinic, finasteride prices start from £24.99.

Every price includes the prescription, the consultation, the packaging, and delivery. There are no hidden fees.

What happens when you order from OnlineClinic

Our process is straightforward. From start to finish, this is what happens when you order with us:

  1. Fill in the medical questionnaire. It takes 5 to 10 minutes. The questions are thorough on purpose.
  2. A GMC-registered prescriber reviews your answers. If they need more details, they will message you through your account.
  3. If treatment is approved, it is dispensed and dispatched. Next-day delivery, with the full patient information leaflet included.
  4. If it is not approved, the prescriber explains why. You are not charged for treatment that is not issued.

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Frequently asked questions

How common are finasteride side effects, really?

Does finasteride cause erectile dysfunction?

Does finasteride cause depression or suicidal thoughts?

Is post-finasteride syndrome real?

Will finasteride affect my fertility?

Does finasteride affect a PSA test?

Is topical finasteride safer than tablets?

Can I drink alcohol on finasteride?

Is OnlineClinic safe to use?

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Trial evidence

  • Kaufman KD et al. Finasteride in the treatment of men with androgenetic alopecia (Finasteride Male Pattern Hair Loss Study Group). Journal of the American Academy of Dermatology, 1998. Read the trial
  • Drake L et al. The effects of finasteride on scalp skin and serum androgen levels in men with androgenetic alopecia. Journal of the American Academy of Dermatology, 1999. Read the study
  • Kaufman KD et al. Finasteride in the treatment of men with androgenetic alopecia. Journal of the American Academy of Dermatology, 1998. Read the trial

Product information and regulation

  • MHRA Drug Safety Update: finasteride and dutasteride, updated safety warnings for psychiatric side effects and sexual dysfunction, 11 May 2026. Read the update
  • MHRA press announcement: strengthened safety warnings for finasteride and dutasteride, 11 May 2026. Read the announcement
  • MHRA Drug Safety Update, April 2024: reminder of the risk of psychiatric side effects and of sexual side effects which may persist after stopping (patient cards introduced). Read the update
  • EMA, Article 31 referral: suicidal thoughts confirmed as a side effect of finasteride tablets, no direct link for dutasteride. PRAC 8 May 2025 (EMA/142716/2025). Read the PRAC outcome
  • EMA, final referral outcome endorsed by the CMDh on 19 June 2025, European Commission decision 22 August 2025 (EMA/202053/2025). Read the final outcome
  • Summary of Product Characteristics, Propecia 1mg film-coated tablets (Organon Pharma UK), sections 4.1 to 4.8. Read the SmPC
  • Summary of Product Characteristics, Finasteride 1mg tablets (generic), sections 4.1 to 4.8. Read the SmPC
  • General Pharmaceutical Council: update on the provision of finasteride. Read the GPhC update
  • FDA alert on compounded topical finasteride products, 22 April 2025. Read the alert
  • MHRA Yellow Card scheme, for reporting any suspected side effect. Report a side effect

Medically reviewed by Dr. Anup Jethwa, Clinical Lead

GMC Reg. #7138282 · Last reviewed: 15-09-2026 · Next review: 12-07-2027

Disclaimer

Finasteride is a prescription-only medicine for men. It is not licensed for women and must not be taken by anyone under 18. Whether it is suitable for you is decided by a GMC-registered prescriber based on your individual medical history. The information here is for general guidance and is not a substitute for professional medical advice.

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