> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hi-doctor.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Finasteride — how it works, evidence and side effects

> Finasteride: a daily 1 mg tablet authorised in the EU for male pattern hair loss since 1999. How it works, the trial evidence and reported side effects.

Finasteride is a daily 1 mg tablet, and one of the few hair-loss medicines formally authorised for this purpose in EU countries. It works by lowering DHT, a hormone made from testosterone that gradually shrinks hair follicles in male pattern hair loss. It is authorised for men only, and it is not for women.

## What it is

Finasteride is a 5-alpha-reductase inhibitor — specifically a 4-azasteroid 5-alpha-reductase inhibitor, taken as a 1 mg film-coated tablet. It reduces the conversion of testosterone into DHT, the hormone responsible for follicle miniaturisation in male androgenetic alopecia.

<Info>
  Active ingredient: **finasteride**. Dosage: **1 mg once daily**, with or without food. It is a continuous daily treatment — on discontinuation, effects fade over 6–12 months.
</Info>

## How it works

<CardGroup cols={3}>
  <Card title="DHT shrinks the hair follicle" icon="atom">
    Male pattern hair loss is driven by dihydrotestosterone (DHT), a hormone the body makes from testosterone. A balding scalp contains miniaturised follicles and higher amounts of DHT, so each growth cycle produces a thinner, shorter hair until visible growth stops.
  </Card>

  <Card title="Finasteride blocks the converting enzyme" icon="lock">
    It blocks the type II 5-alpha-reductase enzyme that turns testosterone into DHT, so less DHT reaches the scalp.
  </Card>

  <Card title="Scalp DHT falls, follicles recover" icon="seedling">
    With less DHT reaching the scalp, the miniaturisation process is opposed and follicles can recover over time.
  </Card>
</CardGroup>

## EU authorisation

Finasteride has been authorised for use in the EU since **1 February 1999** (AEMPS CIMA, Propecia 1 mg film-coated tablets, Spain registration 62441), so a licensed doctor can prescribe it when it is clinically appropriate.

## What the studies reported

The trials behind finasteride (Kaufman et al., *J Am Acad Dermatol* 1998, PMID 9777765) enrolled only men aged 18–41 with vertex-pattern hair loss. They did not establish an effect on bitemporal recession or late-stage hair loss, and the EU product information states that continued use is needed to keep the benefit.

## What has been reported

The figures below compare finasteride 1 mg with placebo, as reported in the EU Summary of Product Characteristics (SmPC, section 4.8).

| Reaction                                           | Finasteride 1 mg | Placebo | EU SmPC frequency                 |
| -------------------------------------------------- | ---------------- | ------- | --------------------------------- |
| Sexual adverse reactions overall (first 12 months) | 3.8%             | 2.1%    | —                                 |
| Sexual adverse reactions (years 2–5, ongoing)      | 0.6%             | —       | —                                 |
| Decreased libido                                   | 1.8%             | 1.3%    | Uncommon (1 in 1,000 to 1 in 100) |
| Erectile dysfunction                               | 1.3%             | 0.7%    | Uncommon                          |
| Ejaculation disorder (reduced ejaculate volume)    | 0.8%             | 0.4%    | Uncommon                          |

About 1% of men in each group (finasteride and placebo) stopped treatment for a sexual side effect in the first 12 months.

<AccordionGroup>
  <Accordion title="Sexual dysfunction that persists after stopping">
    Persistence of decreased libido, erectile dysfunction and ejaculation disorders after finasteride is stopped has been reported in post-marketing use. Frequency is not known, because these are spontaneous reports.
  </Accordion>

  <Accordion title="Depression, anxiety and suicidal ideation">
    Depression is listed as uncommon; anxiety and suicidal ideation are listed with frequency not known. After an EU-wide Article 31 review (started October 2024, European Commission decision August 2025), suicidal ideation was confirmed as a side effect of finasteride 1 mg and 5 mg tablets at an unknown frequency, and a patient card is now included in 1 mg packs. Anyone who experiences mood changes should seek medical advice and, on finasteride 1 mg, stop treatment.
  </Accordion>

  <Accordion title="Male breast cancer">
    Reported during post-marketing use; frequency cannot be estimated from the available data.
  </Accordion>

  <Accordion title="Contraindicated in women">
    The EU product information contraindicates use in women, because finasteride can cause abnormalities of the external genitalia in a male foetus if taken during pregnancy.
  </Accordion>
</AccordionGroup>

## A steady, monitored routine

<Steps>
  <Step title="Months 1–3">
    Daily 1 mg tablet; changes build silently.
  </Step>

  <Step title="Months 3–6">
    Shedding stabilises.
  </Step>

  <Step title="Months 6–12">
    Visible improvement is assessed.
  </Step>

  <Step title="Ongoing">
    Continuous use with periodic reviews.
  </Step>
</Steps>

## Who it is not suitable for

Finasteride is authorised for adult men with male pattern hair loss only — it is not authorised for women or people under 18.

## How Hi-Doctor handles it

A licensed doctor confirms the diagnosis, reviews the risks, and rules out contraindications before prescribing. The medicine itself is paid separately at a pharmacy; the [pricing page](/essentials/pricing) covers what the consultation fee includes.

## Sources

* AEMPS CIMA — Propecia 1 mg comprimidos recubiertos, ficha técnica (Spain, registration 62441, authorised 1 February 1999)
* emc — Propecia 1 mg Film-Coated Tablets, Summary of Product Characteristics
* EMA — Article 31 referral: finasteride- and dutasteride-containing medicinal products
* Kaufman et al., *J Am Acad Dermatol* 1998 (PMID 9777765)

## Related reading

* [Minoxidil — how it works and evidence](/library/medicines/minoxidil)
* [Androgenetic alopecia](/library/conditions/androgenetic-alopecia)
* [Safety and eligibility](/essentials/safety)

## Start a consultation

<Card title="Hair-growth consultation" icon="stethoscope" href="https://hi-doctor.ai/consultation/hair-growth/1">
  Answer the hair-growth questionnaire and a registered doctor reviews it.
  They decide whether treatment is appropriate, which one, and at what dose —
  and declining is a normal outcome. See [what it costs](/essentials/pricing)
  and [how the review works](/essentials/how-it-works).
</Card>

<Warning>
  This page is reference information, not medical advice and not a prescription. Whether a medicine is appropriate for you is decided by a registered doctor after reviewing your consultation.
</Warning>