Finasteride Side Effects: UK Patient Guide

Q: Do finasteride side effects go away?

For most men, side effects are temporary. In placebo-controlled trials, sexual side effects resolved in the majority of men who continued treatment and in virtually all men who stopped. Persistent side effects after stopping are documented but appear to be uncommon based on available data.

Q: Can I get a Yellow Card report from my GP?

Yes. Your GP can submit a Yellow Card report on your behalf, or you can submit one yourself at yellowcard.mhra.gov.uk. You do not need a GP's approval to submit your own report.

Q: Is finasteride safe long-term in the UK?

Long-term safety data (up to 10 years) from the PCPT trial and extensions of the AGA key trials suggest no new safety signals emerge with continued use. The MHRA benefit/risk assessment for licensed indications remains positive. See our long-term safety guide for the full evidence.

Information sourced from the MHRA-approved Propecia Summary of Product Characteristics (SmPC) and the electronic Medicines Compendium (eMC). Reviewed by our medical board. | Back to UK hub

Most men who take finasteride tolerate it well. The most commonly reported side effects affect sexual function in a minority of users; the majority of these resolve spontaneously on continued treatment or after stopping.

Side effects by MHRA frequency category

The MHRA-approved SmPC for Propecia (finasteride 1 mg) uses standard EU/EEA frequency categories:

Category	Definition	Reported side effects
Common	≥1/100, <1/10 (affects up to 1 in 10)	Decreased libido, erectile dysfunction, ejaculation disorders (ejaculatory dysfunction, decreased volume)
Uncommon	≥1/1,000, <1/100 (affects up to 1 in 100)	Breast tenderness or enlargement (gynaecomastia), depression, anxiety, hypersensitivity reactions (swelling of lips/face/throat)
Rare	≥1/10,000, <1/1,000	Testicular pain, palpitations
Not known	Cannot be estimated from available data	Persistent sexual dysfunction after stopping (see below); suicidal ideation

Source: MHRA-approved Propecia 1 mg SmPC, eMC 2024. Frequencies based on phase-III clinical trial data and post-marketing surveillance.

Sexual side effects: what the evidence shows

In key 2-year placebo-controlled trials (Kaufman 1998), the rate of sexual adverse effects on finasteride 1 mg was low:

Side effect	Finasteride 1 mg	Placebo
Decreased libido	1.8%	1.3%
Erectile dysfunction	1.3%	0.7%
Ejaculation disorders	1.2%	0.7%

Source: Kaufman KD et al. J Am Acad Dermatol 1998; integrated analysis of phase-III trials. Discontinuation due to sexual AEs: finasteride 1.2% vs placebo 0.9%.

Resolution rates were high: in men who discontinued finasteride, sexual function returned to baseline in the majority within 3-12 months.

Post-finasteride syndrome (PFS)

MHRA position: The MHRA issued Drug Safety Updates in May 2017 (depression and, in rare cases, suicidal thoughts) and April 2024 (sexual dysfunction that may persist after stopping, plus a patient card in all finasteride packs). These are rare events but the MHRA considers the benefit/risk balance to remain positive for the licensed indications.

Post-finasteride syndrome (PFS) is a term used to describe a constellation of persistent sexual, neurological, and physical symptoms that some patients report after stopping finasteride. The estimated prevalence remains uncertain (studies range from very rare to a few percent), and a clear biological mechanism has not been established. If you experience symptoms you believe are related to finasteride, discuss with your GP or dermatologist.

Mood and mental health: UK warnings

The MHRA issued a Drug Safety Update in May 2017 on rare reports of depression and suicidal thoughts with finasteride. Depression and anxiety are listed as uncommon side effects. Its April 2024 update advised asking patients about any history of depression or suicidal ideation before prescribing.

If you experience low mood, anxiety, or thoughts of self-harm while taking finasteride:

Contact your GP promptly
Call Samaritans on 116 123 (free, 24/7)
Report the reaction to the MHRA Yellow Card scheme (see below)

Reporting side effects: MHRA Yellow Card

UK patients and healthcare professionals can report suspected adverse reactions from finasteride directly to the MHRA via the Yellow Card scheme:

Online: yellowcard.mhra.gov.uk
By phone: 0800 731 6789 (freephone, Mon-Fri 9am-5pm)
Via the Yellow Card app (iOS/Android)

Yellow Card reports from UK patients directly contribute to MHRA signal detection and label updates. They are taken seriously and do not require certainty that the drug caused the reaction.

Prostate-specific antigen (PSA) and finasteride

Finasteride reduces serum PSA by approximately 41% after 6+ months at 1 mg/day. UK GPs and urologists monitoring PSA in men on finasteride must apply a correction factor. See the PSA section on our UK hub for the correction formula.

Frequently asked questions

Do finasteride side effects go away?

For most men, side effects are temporary. In placebo-controlled trials, sexual side effects resolved in the majority of men who continued treatment and in virtually all men who stopped. Persistent side effects after stopping are documented but appear to be uncommon based on available data.

Can I get a Yellow Card report from my GP?

Yes. Your GP can submit a Yellow Card report on your behalf, or you can submit one yourself at yellowcard.mhra.gov.uk. You do not need a GP’s approval to submit your own report.

Is finasteride safe long-term in the UK?

Long-term safety data (up to 10 years) from the PCPT trial and extensions of the AGA key trials suggest no new safety signals emerge with continued use. The MHRA benefit/risk assessment for licensed indications remains positive. See our long-term safety guide for the full evidence.

Sources: MHRA Propecia SmPC (eMC, 2024). Kaufman KD et al. JAAD 1998;39(4):578-589. MHRA Drug Safety Updates: Finasteride (May 2017; April 2024). NICE CKS: Alopecia (2023).