Propecia (Finasteride) for Hair Loss: How It Works and What to Expect

Propecia is the branded name for finasteride 1mg, a prescription tablet used to treat male pattern baldness in men. It works by blocking the hormone that shrinks hair follicles, and clinical trials show it stops hair loss in the majority of men who take it. This article is for adult men (18 and over) only. Women who are losing hair should speak to their GP, as finasteride is not appropriate for women and must not be handled by anyone who is pregnant or may become pregnant.

What Propecia actually does at the follicle level#

Male pattern baldness happens when a hormone called dihydrotestosterone (DHT) gradually miniaturises hair follicles. Your body makes DHT by converting testosterone using an enzyme called 5-alpha reductase. If your follicles are genetically sensitive to DHT, they shrink over time, producing thinner hairs until they stop producing hair altogether.

Finasteride blocks that enzyme. At the 1mg dose used in Propecia, it reduces scalp DHT by roughly 60% and serum (blood) DHT by roughly 65%, based on trial data from the pivotal studies. Less DHT means less pressure on sensitive follicles. It does not regrow a bald scalp, but it can slow or stop further loss and, in some men, produce modest regrowth.

You can read more about the hormone involved in our guide to DHT and hair loss.

Which stage of hair loss responds best#

Finasteride works best for men with early to moderate hair loss, roughly stages II to IV on the Norwood scale. Stage II is a mild recession at the temples; stage IV is more noticeable thinning at the crown with a clear gap between the front and top. Men with extensive loss (stages V to VII, where large areas of the scalp are bare) are less likely to see meaningful benefit, because the follicles in those areas have already stopped functioning.

If you are noticing early thinning at the crown or a gradually receding hairline, that is when finasteride is most useful. The earlier you start, the more hair there is to preserve.

Does it actually work?#

Yes, with some caveats. In the pivotal randomised controlled trial, 83% of men taking finasteride 1mg maintained their hair count at two years, compared with 28% in the placebo group. Around 66% saw actual improvement in hair growth. A longer-term Japanese cohort study followed 523 men for 10 years and reported sustained benefit in around 99% of participants; however, this figure should be interpreted with considerable caution, as the study was open-label and uncontrolled, with a selected patient population, and is not directly comparable to RCT data. A UK clinician would not rely on it as strong evidence of long-term efficacy.

Overall, finasteride is one of the most evidence-backed treatments for male pattern baldness currently available.

How long before you see results#

Give it time. Most men do not see any visible change in the first three months. This is normal: the drug is slowing down a gradual process, and the hair growth cycle means changes take months to show. The usual guidance is to continue for at least 12 months before judging whether it is working. Some men see improvement at six months; others take longer.

Our separate article on how long finasteride takes to work covers the timeline in more detail.

Propecia vs generic finasteride#

Propecia (branded) and generic finasteride 1mg contain exactly the same active ingredient at the same dose. The only difference is price. Branded Propecia costs considerably more. Generic finasteride is widely available in the UK from GPhC-registered online pharmacies. At Totiva, for example, a 28-tablet pack of finasteride 1mg costs £14.99 and an 84-tablet pack costs £41.99, both requiring a prescription from a UK-registered clinician.

Finasteride is not available on the NHS for hair loss. Because male pattern baldness is classified as a cosmetic condition rather than a clinical one, NHS prescriptions are not issued for this use. You will need a private prescription, either from your GP (who may charge a private consultation fee) or through a regulated online pharmacy.

Combining finasteride with minoxidil#

Many men use both. Finasteride reduces DHT. Minoxidil works differently: it directly stimulates the follicle and extends the hair's active growth phase. Because they act through separate pathways, the combination produces better results than either alone. A randomised trial comparing the combination with monotherapy found significantly greater hair counts at 12 months in the combination group. If you are considering both, see our guide on using finasteride and minoxidil together.

Side effects to know about#

Side effects are uncommon but real. In the pivotal RCT, decreased libido was reported in approximately 1.8% of men on finasteride and erectile dysfunction in approximately 1.3%, compared with 1.3% and 0.7% respectively in the placebo group. Ejaculation disorders were also reported in a small number of men.

In June 2023, the MHRA updated the UK product labelling for finasteride to include depression and suicidal ideation as recognised risks. If you experience low mood, anxiety or any change in mental wellbeing while taking finasteride, speak to a doctor promptly.

A small number of men report sexual or other side effects that continue after stopping the drug. This is known as Post-Finasteride Syndrome (PFS). The mechanisms are not fully understood. Whilst PFS is not formally defined in all clinical guidelines, the EMA and NHS patient information acknowledge that persistent adverse effects have been reported and take them seriously. You can read a fuller discussion in our article on Post-Finasteride Syndrome, and on finasteride side effects more broadly.

High-grade prostate cancer: The MHRA product information for finasteride notes a potential association between 5-alpha reductase inhibitors and high-grade prostate cancer. Although a causal relationship has not been established, your prescribing clinician should be aware of your prostate health history before starting treatment.

Pregnancy warning: Finasteride must not be taken by women. Women who are pregnant or who may become pregnant must not handle crushed or broken tablets, as the active ingredient can be absorbed through skin and may cause abnormal development of a male fetus's genitalia.

Fertility#

Sperm parameter changes, including reduced sperm count and motility, have been reported in men taking finasteride. For most men these appear to be reversible after stopping, but reversibility cannot be guaranteed in all cases. If you are actively trying to conceive, or thinking about it in the near future, discuss this with a clinician — ideally a urologist or andrologist — before starting finasteride rather than waiting until it is urgent. Any suspected effects on fertility should be reported to the MHRA via the Yellow Card scheme.

The PSA interaction#

Finasteride reduces prostate-specific antigen (PSA) levels by approximately 50% after around six months of continuous use, though the degree of suppression can vary depending on dose and duration of treatment. PSA is a screening marker sometimes used to detect prostate problems. If you have a PSA test while taking finasteride and your result looks low, it may not reflect your true level. Tell any clinician requesting the test that you are on finasteride so they can interpret the result correctly. Your prescribing clinician will advise on whether a baseline PSA reading is appropriate for you.

What happens if you stop#

The benefits are not permanent. If you stop taking finasteride, DHT levels return to normal within about two weeks, and most of the hair gained or preserved will be lost within 9 to 12 months. Finasteride is a long-term treatment. If you are considering stopping, speak to a clinician first.

How to get it in the UK#

You need a prescription. Your options are a private GP consultation, a CQC-registered private clinic, or a GPhC-registered online pharmacy. When using an online service, check that it is GPhC-registered before sharing any health information or making a payment. Totiva's hair loss service offers a free online consultation with UK-registered clinicians, and you only pay if treatment is approved.