Finasteride: how it works

How does Finasteride work to treat pattern hair loss?

Pattern hair loss is driven by DHT, a potent androgen converted from testosterone by the enzyme 5-alpha reductase, which progressively shortens the growth phase in susceptible follicles until hair stops being visible. Finasteride inhibits type II 5-alpha reductase, substantially reducing DHT, which slows miniaturisation and in many men allows partial recovery.

What did the clinical trials show about Finasteride's effectiveness?

Registration studies followed men with vertex hair loss over one and two years and found Finasteride produced clinically significant hair-count increases while placebo groups kept losing hair; five-year follow-up showed the improvement held. Much of the benefit is loss prevented compared with no treatment, rather than hair regained.

The registration studies followed men with vertex hair loss over one and two years. Finasteride produced clinically significant increases in hair count in the treated area, while the placebo groups continued to lose hair, and improvement was seen across multiple assessment methods.

Longer follow-up over five years showed durable improvement against placebo, with the placebo group's progressive loss continuing. Separate work found the drug increases the proportion of hairs in the growth phase.

The comparison that matters is not against your current state but against where you would be without treatment. Much of the benefit is loss prevented rather than hair regained.

What does Finasteride not do?

Finasteride does not regrow hair from areas that are genuinely bare, where follicles are gone, and it works better on the vertex and mid-scalp than elsewhere. It does not act quickly, since the earliest meaningful assessment is months, not weeks, and it does not cure anything: the effect depends on continued use.

• It does not regrow hair from areas that are genuinely bare, where follicles are gone
• It does not work everywhere equally; evidence is strongest for the vertex and mid-scalp
• It does not act quickly; the earliest meaningful assessment is months, not weeks
• It does not cure anything; the effect depends on continued use

What are the practical points to know before starting Finasteride?

Finasteride is taken daily, with the accepted assessment point at around six to twelve months. Some men notice increased shedding in the first few weeks as follicles cycle, which is not a sign of failure. It is not prescribed to women; non-surgical alternatives exist for them instead.

Our guide to non-surgical treatment covers the alternatives, and the article on stopping Finasteride covers what happens if you discontinue.

Sources

1. Kaufman KD, et al. Finasteride in the treatment of men with androgenetic alopecia. Finasteride Male Pattern Hair Loss Study Group. Journal of the American Academy of Dermatology, 1998. pubmed.ncbi.nlm.nih.gov/9777765
2. Long-term (5-year) multinational experience with Finasteride 1 mg in the treatment of men with androgenetic alopecia. European Journal of Dermatology, 2002. pubmed.ncbi.nlm.nih.gov/11809594
3. Gupta AK, Venkataraman M, Talukder M, Bamimore MA. Finasteride for hair loss: a review. Journal of Dermatological Treatment, 2022;33(4):1938-1946. pubmed.ncbi.nlm.nih.gov/34291720

This article summarises published research. It is general educational information, not medical advice, and it is not a recommendation to start, stop or change any medication. Prescription drugs carry contraindications and interactions; discuss them with a doctor who knows your medical history.