How does finasteride work?
Finasteride is a 5-alpha-reductase inhibitor, a medication linked to blocking the enzyme that converts testosterone into dihydrotestosterone (DHT). The hormone is associated with follicle miniaturisation in male pattern hair loss. With less DHT in the scalp, the signal that drives this miniaturisation of hair follicles may be reduced (5).
Finasteride may slow hair loss and support hair regrowth. It’s taken as a 1 mg oral tablet, usually once daily. Its effects depend on individual factors, and results vary (5).
Who may use finasteride, and who may not?
Prescription haircare treatments are available following a consultation with a doctor to assess suitability.
Finasteride may suit some adult men who experience male pattern hair loss, including a receding hairline, hair thinning or hair loss concerns. People respond differently, and a registered health practitioner will assess whether it is appropriate.
Finasteride may not suit:
- Those who are or may become pregnant or who are breastfeeding, even if you experience female pattern hair loss (handling or use may pose a risk to a developing male foetus) (8).
- People under 18 years of age.
- Anyone with a known allergy or sensitivity to finasteride.
- Anyone with a history of certain medical conditions, including liver problems, should discuss their medical history with a doctor.
- Anyone taking other medicines in the same class (5-alpha-reductase inhibitors, such as dutasteride).
Side effects are possible; consult a doctor to discuss risks.
How is finasteride used?
Finasteride must be prescribed by a doctor or registered health practitioner. Your registered health practitioner will advise you on the recommended dosage and instructions. The information below is general in nature and does not constitute medical advice.
- Finasteride is usually taken as one tablet daily, as prescribed (5).
- Taking more than the recommended amount may not improve results and may increase the risk of potential side effects.
- Hair restoration is a gradual process, with results varying over time. Always speak to your registered health practitioner before stopping finasteride.
- If treatment is stopped, any hair that was maintained may be lost over the following months; responses differ between individuals (5).
- Those who are pregnant, or may become pregnant, must not handle broken finasteride tablets or take finasteride.
Possible side effects
Side effects are possible; consult a doctor to discuss risks before starting any prescription haircare medication.
Individual experiences vary. Reported potential side effects in men include (2, 3, 5):
- Impact on sexual function, including decreased libido or erectile dysfunction.
- Skin rash or allergic reaction.
- Breast tenderness or enlargement.
- Changes to mood, anxiety or psychological well-being.
Following reviews of safety data, suicidal ideation has been recognised as a possible adverse reaction associated with oral finasteride. Any mood changes should be discussed with a doctor promptly (2).
Some side effects may resolve after stopping the medicine, but some men have reported effects that persisted; experiences vary (4).
Finasteride must not be handled or used by women who are or may become pregnant, as it may affect the development of a male foetus (5). Seek medical advice from a doctor immediately if you develop any concerning symptoms, in particular a rash, swelling, or trouble breathing that could suggest a serious allergic reaction.
How long does finasteride take to work?
Hair restoration is a gradual process, with results varying over time.
Because finasteride acts on hormones, individual experiences may vary. Clinical trials have generally assessed outcomes over periods of several months to a year, with many participants showing stabilisation or improvement of hair loss.
One study on around 1,500 men aged 18–41 with typical male pattern hair loss (mainly on the crown), saw the following results after taking 1 mg of finasteride for 1 year (9):
- The men themselves reported that their hair loss slowed, they saw more hair, and their hair looked better overall.
- Doctors looking at them in the clinic rated their hair as improved compared with before treatment.
- An independent panel looking at standardised scalp photos of those who took finasteride and those who took a placebo tablet could also see a visible difference in favour of finasteride.
- Men on finasteride had around 100 more hairs in the crown circle compared with the placebo group.
These are population-level findings and cannot be applied to any individual case (5).
