Finasteride Side Effects: The Evidence Explained
A balanced, evidence-based look at finasteride's side effects — how common they really are, the 2025 mood-change warning, post-finasteride syndrome, and when to stop.
Part of the Male Hair Loss Health Guide.
Key fact: Most men take finasteride without side effects. The most discussed effects are sexual, reported in around 1–2% of users at the 1mg dose and usually reversible — but a rare risk of mood changes is now formally recognised, so it is worth understanding the full picture before you start.
Discuss Finasteride with a Prescriber
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Start Consultation →How common are side effects?
It helps to start with perspective. Finasteride has been in clinical use for over 25 years and is taken by millions of men. In the licensing trials, side effects were uncommon and, in most cases, reversible — and the rates in the finasteride group were often only slightly higher than in the placebo group, which tells you that some reported effects were not caused by the drug at all.
1–2%
Reported sexual side effects at the 1mg dose
25+
Years of clinical use and monitoring
Most
Men experience no side effects at all
Sexual side effects
These are the effects finasteride is best known for. At the 1mg hair loss dose they include:
- Reduced libido — a drop in sex drive, reported in around 1–2% of users
- Erectile dysfunction — difficulty getting or keeping an erection, similarly uncommon
- Reduced ejaculate volume — a smaller volume of semen, generally not affecting fertility for most men
The mechanism is thought to relate to lower DHT, which plays a role in sexual function as well as hair loss. Importantly, the 1mg hair loss dose is five times lower than the 5mg dose used for prostate enlargement, and the great majority of men who experience these effects find they resolve either on stopping the medicine or over continued use.
Mood changes and the 2025 EMA warning
2025 regulatory update: the European Medicines Agency confirmed that depression and, very rarely, suicidal thoughts can be associated with finasteride. This is now recognised in the product information. It is a rare effect — but a serious one, which is why it is worth knowing about before you start.
What this means in practice: if you notice low mood, depression or any thoughts of self-harm while taking finasteride, stop the medicine and speak to a doctor promptly. Men with a history of depression should raise this with a prescriber before starting, so the decision can be made with that context in mind.
Post-finasteride syndrome
You may come across the term post-finasteride syndrome (PFS) online. It refers to a cluster of sexual, physical and psychological symptoms that a small number of men report continuing after they stop finasteride, rather than resolving as expected.
The honest scientific position is that PFS is uncommon and remains debated. It has not been consistently demonstrated in controlled studies, and it is difficult to separate from other causes. That does not mean the experiences reported are not real for those affected — it means the evidence base is not yet settled. Anyone concerned about symptoms persisting after stopping should seek an individual medical assessment rather than rely on online accounts.
Other and rare side effects
| Side effect | Notes |
|---|---|
| Breast tenderness or enlargement | Uncommon. Report any breast lumps, pain or discharge to a doctor, as these need checking. |
| Skin rash / allergic reaction | Rare. Stop and seek advice if you develop a rash, swelling or difficulty breathing. |
| Testicular discomfort | Uncommon and usually mild. |
| PSA blood test effect | Finasteride can lower PSA readings; tell any doctor doing a prostate check that you take it. |
Not for women: finasteride must not be taken or handled by women who are pregnant or may become pregnant, because it can cause abnormalities in a developing male baby. Keep tablets sealed and stored away from women and children.
When to stop and seek advice
Stop finasteride and contact a doctor if you experience any of the following:
- Low mood, depression, or any thoughts of self-harm
- Sexual side effects that trouble you or do not settle
- A lump, pain, tenderness or discharge from the breast tissue
- Signs of an allergic reaction — rash, swelling of the face or throat, difficulty breathing
Bear in mind: stopping finasteride also means the DHT suppression ends, so hair loss will resume within 6–12 months. If you are stopping because of side effects, discuss alternatives such as topical minoxidil with your prescriber.
Weighing up the decision
For most men, finasteride offers a large, well-evidenced benefit — it is the most effective oral treatment for male pattern hair loss — against a low and mostly reversible risk of side effects. But "most men" is not "all men", and the right call depends on your own priorities, medical history and how you weigh the small risks. That is exactly the conversation a prescriber is there to have.
Talk It Through Before You Start
Complete a short online consultation and our GPhC-registered pharmacist independent prescribers will assess whether finasteride is a safe and suitable choice for you.
Start Consultation →Frequently Asked Questions
What are the most common side effects of finasteride?
Finasteride is well tolerated by most men. The most discussed effects are sexual — reduced libido, erectile dysfunction and reduced ejaculate volume — each reported in around 1 to 2% of users at the 1mg hair loss dose in clinical trials. When they occur they usually resolve on stopping the medicine or over time.
Does finasteride cause permanent sexual side effects?
For the large majority of men, sexual side effects resolve on stopping finasteride. A small number of men report symptoms that persist after stopping — sometimes called post-finasteride syndrome — but this is uncommon and not yet clearly established or quantified in large-scale studies. Discuss any persistent symptoms with a doctor.
Can finasteride affect mood?
In 2025 the European Medicines Agency confirmed that depression and, very rarely, suicidal thoughts can be associated with finasteride. This is a rare effect, but if you notice changes in mood while taking it you should stop and speak to a doctor promptly. Men with a history of depression should discuss finasteride carefully with a prescriber first.
What is post-finasteride syndrome?
Post-finasteride syndrome is a term used for sexual, physical or psychological symptoms that some men report continuing after they stop finasteride. It is uncommon and remains debated, as it has not been consistently demonstrated in controlled studies. Anyone concerned about persistent symptoms should seek medical assessment.
When should I stop taking finasteride?
Stop and speak to a doctor if you develop changes in mood or depression, sexual side effects that trouble you or do not settle, breast lumps, tenderness or discharge, or any allergic reaction. Remember that stopping finasteride also means hair loss will resume within 6 to 12 months, so weigh this up with your prescriber.
Are finasteride side effects a reason not to take it?
For most men the risk of side effects is low and reversible, and finasteride remains the most effective oral treatment for male pattern hair loss. Whether the balance of benefit and risk is right for you is an individual decision, best made with a prescriber who knows your medical history.
References
- European Medicines Agency. Finasteride and dutasteride: risk of mood changes and sexual dysfunction. 2025. ema.europa.eu
- electronic medicines compendium (emc). Finasteride 1mg tablets — Summary of Product Characteristics. medicines.org.uk
- Kaufman KD, et al. Finasteride in the treatment of men with androgenetic alopecia. Journal of the American Academy of Dermatology. 1998;39(4):578–589. pubmed.ncbi.nlm.nih.gov
- MHRA. Finasteride: reminder of the risk of psychiatric side effects. Drug Safety Update. gov.uk
- NHS. Finasteride. nhs.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. Finasteride is a prescription-only medicine — always complete a medical consultation before starting treatment. This article touches on mood and mental health; if you are struggling, please speak to a doctor or a trusted person, and in a medical emergency call 999.