Finasteride Side Effects: UK Safety Guide for Hair Loss
Finasteride is an established prescription treatment for male pattern hair loss, but its potential sexual and psychiatric adverse effects need to be understood before treatment starts.
This guide explains recognised finasteride side effects, current UK safety advice, what is known about persistent symptoms, and how topical finasteride differs from oral finasteride without implying that a scalp-applied route is risk-free.
What Are the Side Effects of Finasteride?
Finasteride inhibits 5-alpha-reductase and reduces dihydrotestosterone (DHT). Because DHT reduction is systemic with oral finasteride, adverse effects can involve sexual function, mood and other body systems. The exact likelihood depends on the adverse effect and the evidence source.
Sexual side effects
- Reduced libido
- Erectile dysfunction
- Ejulation disorders, including reduced ejaculate volume
- Sexual dysfunction has also been reported after treatment has stopped
Psychiatric effects
- Depressed mood
- Depression
- Anxiety has been reported
- Suicidal ideation is included in UK safety information
Other reported effects
- Breast tenderness or enlargement
- Testicular pain
- Hypersensitivity reactions
- Fertility concerns have been reported in post-marketing use
Important UK safety advice
The MHRA advises that patients prescribed finasteride 1 mg should stop taking the medicine if they develop depression or suicidal thoughts and contact a healthcare professional as soon as possible.
Patients experiencing sexual dysfunction should contact their healthcare professional for medical advice.
How Common Are Finasteride Side Effects?
There is no single useful percentage that describes every finasteride side effect. In the UK Summary of Product Characteristics for finasteride 1 mg, decreased libido, erectile dysfunction and ejaculation disorder are listed as uncommon adverse effects. Some post-marketing events have an unknown frequency because spontaneous reports cannot reliably establish how often they occur.
| Safety issue | UK product information context | Practical meaning |
|---|---|---|
| Reduced libido | Listed as uncommon in finasteride 1 mg product information. | Discuss new or persistent changes in sexual function with the prescriber. |
| Erectile dysfunction | Listed as uncommon in finasteride 1 mg product information. | Symptoms should be clinically reviewed rather than automatically attributed to one cause. |
| Depression | Included in current UK safety information. | Mood changes warrant prompt clinical discussion. |
| Suicidal ideation | Frequency cannot be reliably estimated from post-marketing reports. | This is a serious safety signal. Follow current MHRA advice immediately if symptoms occur. |
| Persistent sexual dysfunction | Current MHRA advice states sexual dysfunction may persist after treatment is stopped. | Persistent symptoms should be medically assessed. |
Can Finasteride Side Effects Continue After Stopping?
Current UK safety advice recognises reports of sexual dysfunction that may persist after finasteride is stopped. This does not mean that persistent symptoms occur in every person who experiences a sexual adverse effect, and post-marketing reports cannot by themselves establish an individual person’s cause.
Persistent symptoms deserve clinical review
If sexual, psychiatric or other symptoms continue after treatment has stopped, speak with a healthcare professional. Persistent symptoms should not be dismissed, but they also should not be self-diagnosed solely from information found online.
Topical vs Oral Finasteride Side Effects
Oral and topical finasteride use the same active medicine, but exposure can differ according to dose, formulation and route. A Phase III study of a specific topical finasteride spray reported markedly lower plasma finasteride concentrations and a smaller reduction in serum DHT than oral finasteride.
Oral Finasteride
Oral finasteride produces systemic exposure and has the longest-established hair-loss evidence base. Sexual and psychiatric adverse-effect warnings in current UK product information remain directly relevant.
Compare Topical vs OralTopical Finasteride
Some studied topical formulations have produced lower systemic exposure than oral treatment. That does not mean every topical formulation has identical absorption or that systemic side effects are impossible.
Explore Topical FinasterideDo not treat “topical” as a synonym for “no systemic risk”
Concentration, application volume, frequency, vehicle and total delivered dose all affect exposure. Evidence from one proprietary research formulation should not automatically be extrapolated to every compounded topical formula.
What Should Be Discussed Before Starting Finasteride?
Prescribing should include more than a side-effect checklist
The MHRA specifically advises healthcare professionals to review relevant medical history, ask about previous depression or suicidal ideation and monitor for psychiatric and sexual side effects.
Individual suitability also depends on the indication, age, other medicines, previous treatment, fertility considerations and whether the patient can recognise when to seek help.
Can the Risk of Finasteride Side Effects Be Reduced?
There is no method that guarantees zero adverse effects. The safest approach is appropriate patient selection, informed consent, correct dosing, monitoring and prompt action if symptoms develop.
Use a clinically appropriate route
Oral and topical routes have different exposure profiles. Route choice should be based on evidence, clinical suitability and patient preferences rather than assuming topical treatment is automatically safer.
Use the prescribed dose
More medicine is not automatically more effective. Dose and formulation should reflect the intended treatment plan and available evidence.
Monitor symptoms
New sexual symptoms, mood changes or other concerning effects should be discussed with the prescriber rather than ignored or managed by self-adjusting treatment.
What Does the Evidence Say?
Use the evidence for the formulation actually studied
Oral finasteride has extensive clinical and post-marketing safety data. Topical finasteride also has clinical trial evidence, but systemic exposure varies according to formulation and dose.
For that reason, claims about reduced systemic exposure should be tied to the specific topical research formulation rather than generalised to every topical product.
When Should You Seek Medical Advice?
Contact your healthcare professional promptly
- New or worsening depression
- Sexual dysfunction that is concerning or persistent
- Breast lumps, enlargement, pain or nipple changes
- Any suspected serious adverse reaction
Depression or suicidal thoughts on finasteride 1 mg
Current MHRA advice states that patients taking finasteride 1 mg should stop treatment and contact their healthcare professional as soon as possible if they develop depression or suicidal thoughts.
Explore Related Finasteride Guides
Considering Finasteride but Concerned About Side Effects?
If you prefer to explore a scalp-applied route, view our dedicated topical finasteride treatment page. Your requested treatment is reviewed for clinical suitability before any prescription-only medicine is supplied.
Finasteride Side Effects FAQs
What are the main side effects of finasteride?
Recognised adverse effects include decreased libido, erectile dysfunction and ejaculation disorders. Current UK safety information also includes depression and suicidal ideation, alongside other less common or post-marketing effects.
Are finasteride side effects common?
Some sexual adverse effects are listed as uncommon in UK finasteride 1 mg product information. Other post-marketing effects have an unknown frequency because spontaneous reporting cannot reliably establish incidence.
Can finasteride cause depression?
Yes. Depression and depressed mood are included in current UK safety information, and suicidal ideation has also been reported. Patients taking finasteride 1 mg who develop depression or suicidal thoughts should follow current MHRA advice and seek medical help promptly.
Can sexual side effects persist after stopping finasteride?
The MHRA states that sexual dysfunction may persist after treatment is stopped. Persistent symptoms should be discussed with a healthcare professional.
Is topical finasteride safer than oral finasteride?
A specific Phase III topical spray produced substantially lower plasma finasteride exposure and a smaller reduction in serum DHT than oral finasteride. However, topical use does not mean zero systemic absorption or zero risk, and results from one studied formulation should not automatically be applied to every topical product.
Does topical finasteride still have side effects?
Potential local and systemic adverse effects cannot be excluded. The extent of systemic exposure depends on formulation, dose and application, so topical treatment still requires clinical assessment.
Should I stop finasteride if I have side effects?
Do not make treatment changes solely from general online information. For depression or suicidal thoughts while taking finasteride 1 mg, current MHRA advice is to stop treatment and contact a healthcare professional as soon as possible. Other adverse effects should also be discussed with the prescriber.
Can finasteride affect fertility?
Infertility has been reported during post-marketing use and UK product information includes fertility considerations. Discuss fertility concerns with the prescriber before or during treatment.
Does everyone taking finasteride get side effects?
No. Not everyone experiences adverse effects, and the presence or absence of one effect does not predict every other effect. Individual risk and treatment suitability should be assessed clinically.
Can I use topical finasteride in the UK?
Topical finasteride can be supplied as an unlicensed compounded prescription medicine where a prescriber considers it clinically appropriate. Root & Radiance provides a dedicated topical finasteride assessment pathway.
References
MHRA. Finasteride and Dutasteride: updated safety warnings for psychiatric side effects and sexual dysfunction. Published 11 May 2026. GOV.UK.
Electronic Medicines Compendium. Finasteride 1 mg film-coated tablets, Summary of Product Characteristics. View SmPC.
Piraccini BM et al. Efficacy and safety of topical finasteride spray solution for male androgenetic alopecia: a Phase III, randomized, controlled clinical trial. PubMed.