Male pattern hair loss is common: reviews estimate that it affects around half of white men by the age of 50 (Stough and colleagues, Mayo Clinic Proceedings, 2005). Finasteride is the only oral medication licensed in the UK for it. The questions most patients ask are whether it's right for them, how long it takes, and whether the side effects are worth it.
What causes male pattern hair loss?
Caused by dihydrotestosterone (DHT), a potent androgen derived from testosterone via the enzyme 5-alpha reductase type II. In genetically predisposed men, DHT causes progressive miniaturisation of scalp hair follicles, producing progressively shorter, finer hairs over successive growth cycles until they stop producing visible hair. The pattern follows the characteristic M-shaped recession at the temples and thinning at the crown. Follicles at the back and sides of the scalp are not DHT-sensitive, which is why they remain unaffected.
How does finasteride work?
Finasteride 1mg is a type II 5-alpha reductase inhibitor. Finasteride reduces the conversion of testosterone into DHT, the hormone behind male pattern hair loss. It does not grow new follicles.
What does the clinical evidence show?
The pivotal trials enrolled 1,553 men aged 18 to 41 with male pattern hair loss across two 1-year studies, with 1,215 continuing to a second year (Kaufman KD et al, JAAD 1998. Finasteride Male Pattern Hair Loss Study Group).
Key findings at 2 years:
- In a measured area of balding scalp at the crown, men taking finasteride 1mg had on average 138 more hairs than men on placebo after two years. Individual results vary.
- Placebo group showed progressive hair loss throughout
A systematic review and meta-analysis (Gupta AK et al, J Dermatolog Treat 2022) confirmed finasteride 1mg significantly increased total hair count vs placebo at 24 weeks (mean difference +12.4 hairs/cm²) and 48 weeks (mean difference +16.4 hairs/cm²).
How long does finasteride take to work?
The most important expectation to set correctly.
Generally, three to six months of daily treatment are needed before hair loss stabilises. We check how well it is working at 6 months. If it is working, you can carry on taking it. If it has not helped after a year, we recommend stopping it, and your GP can refer you to a dermatologist if you would like.
Male pattern hair loss usually carries on slowly over time. Treatment works for as long as you keep taking it.
Does finasteride work for frontal hair loss?
The clinical evidence is strongest for vertex (crown) hair loss. The frontal hairline is less responsive, trials showed less consistent benefit in the frontal and parietal scalp compared to the vertex. Many patients see some frontal improvement, but results are more modest and less predictable.
Can you use finasteride with minoxidil?
There is not enough evidence to recommend using finasteride and minoxidil together. If you already use minoxidil, tell our pharmacist during your consultation so they can advise you.
Side effects, the honest picture
Sexual side effects
Uncommon side effects (fewer than 1 in 100 men): lower sex drive, low mood or depression, difficulty getting an erection, and changes in ejaculation, including less semen. Tell our pharmacist or your GP about any side effect, so that a Yellow Card report can be sent to the MHRA.
Post-finasteride syndrome
A subset of patients report persistent sexual, neurological, and psychological symptoms continuing after stopping finasteride. Its existence as a clinical entity is accepted; prevalence and mechanisms remain areas of ongoing research. The FDA added a warning about depression to the finasteride label in 2011. The UK product information warns that low mood, depression and, less often, suicidal thoughts have been reported with finasteride 1mg. If you notice changes in your mood, such as low mood, depression, anxiety or thoughts of suicide, stop taking finasteride and seek medical advice. Patients with a personal or family history of depression or mood disorders should discuss this with their prescribing pharmacist before starting.
Other side effects
Tell your doctor promptly about any changes in your breast tissue, such as lumps, pain or nipple discharge. Women who could become pregnant should not handle crushed or broken finasteride tablets. Finasteride passes into semen in small amounts. Use a condom if your partner is pregnant or could become pregnant. Finasteride lowers PSA, a blood test used to check for prostate cancer. Tell your GP that you are taking finasteride.
Who is finasteride suitable for?
Men aged 18 and over with androgenetic alopecia. Strongest evidence for vertex and crown thinning. Requires daily dosing, with the response assessed at 6 months. Not licensed for women. Contraindicated in women who are pregnant or may become pregnant. Not suitable if you have a rare inherited problem with galactose intolerance, total lactase deficiency or glucose-galactose malabsorption.
What happens if you stop?
If you stop taking it, the benefit begins to reverse by six months and is lost by 9 to 12 months. The gains made during treatment are not permanent without continued DHT suppression. For most patients who respond well, finasteride is a long-term commitment.
Looking after your hair
Stopping smoking, keeping alcohol within recommended limits, eating a balanced diet rich in protein and avoiding stress where you can may all help your hair. You can wash your hair as often as you like. It will not make hair loss worse.
For support, Alopecia UK (alopeciaonline.org.uk) can help, and the British Association of Dermatologists has a patient leaflet.