Finasteride Explained

Written by the Fix My Hair Editorial Team · Clinician-reviewed by Dr Hisham Band · GMC No. 7550130 · Last reviewed 26 Jan 2026

Finasteride is the most effective medical treatment for androgenetic alopecia. It’s also the most misunderstood.

How it works

Finasteride blocks the enzyme 5-alpha reductase, which converts testosterone into DHT — the hormone that shrinks follicles. It reduces scalp DHT by around 70%.

What to expect

It halts progression in roughly 87% of men and often regrows some hair. Give it 3–6 months to show an effect — this is a treatment you judge over seasons, not weeks.

The honest truth on side effects

Side effects affect fewer than 2% of users and are typically reversible on stopping. It’s a prescription medicine that requires a clinician consultation to weigh up properly.

All medications require a clinician consultation before being prescribed.

What finasteride actually is

Finasteride is a prescription medicine, taken as a 1 mg daily tablet for hair loss (the 5 mg version is used for prostate enlargement — a different dose for a different job). It’s one of only two medical treatments with strong, long-term evidence for male pattern hair loss, the other being minoxidil. Crucially, it treats the cause of androgenetic loss rather than masking it, which is why it sits at the centre of most serious medical plans.

How finasteride works

Male pattern hair loss is driven by dihydrotestosterone (DHT), a hormone made when the enzyme 5-alpha-reductase converts testosterone. In men who are genetically sensitive to it, DHT gradually shrinks — or “miniaturises” — follicles until they stop producing visible hair. Finasteride blocks the type II form of that enzyme, cutting scalp DHT by roughly 60–70%. Lower DHT means miniaturisation slows or stalls, giving struggling follicles a chance to recover and keep producing hair.

How effective is it?

Finasteride has some of the best long-term data of any hair-loss treatment. In the large studies that led to its approval, around nine in ten men stopped losing further hair, and roughly two-thirds saw measurable regrowth over one to two years, with the benefit sustained across five years of continued use. In plain terms: for most men it reliably halts progression, and for many it also thickens what’s thinning. It works best on the crown and mid-scalp, and is less predictable at restoring a long-receded hairline — which is where a transplant may be discussed instead.

How to take it — and when you’ll see results

The standard dose is one 1 mg tablet a day, taken consistently. Hair grows slowly, so this is a treatment judged over seasons, not weeks:

• Months 1–3: little visible change; some men notice a temporary increase in shedding as follicles reset — this is normal and passes.
• Months 3–6: shedding settles and loss typically stabilises.
• Months 6–12: regrowth and thickening become visible.
• 12 months and beyond: the full effect, maintained for as long as you keep taking it.

Consistency matters more than the time of day — pick a daily routine you’ll actually stick to.

Side effects: the honest picture

This is what finasteride is most known — and most misunderstood — for. In clinical trials, sexual side effects (reduced libido, erectile or ejaculatory changes) were reported by a small percentage of men, only modestly above placebo, and in most cases resolved either while continuing or after stopping. Less common effects include breast tenderness. A small number of men report persistent symptoms after stopping, sometimes called post-finasteride syndrome; this is uncommon and not fully understood, but it’s one reason the decision deserves a proper conversation rather than a checkout button. The honest summary: side effects are uncommon and usually reversible, but they’re real, and informed consent matters.

Who should — and shouldn’t — take it

Finasteride is licensed for men with male pattern hair loss. It is not for women who are or may become pregnant: DHT is essential to male foetal development, so finasteride can cause birth defects, and pregnant women should not even handle broken or crushed tablets. Most women are therefore treated with different options — see our guide to female hair loss. Anyone with relevant medical history should disclose it at consultation, which is exactly why it’s prescription-only.

Oral versus topical finasteride

Finasteride can also be applied to the scalp as a topical. Topical formulations aim to lower DHT at the scalp while keeping blood levels much lower, which may reduce the risk of systemic side effects while delivering a similar local effect. For men who are cautious about the oral tablet, it’s an increasingly popular middle path — one we can discuss at consultation.

What happens if you stop?

Finasteride maintains its benefit only while you take it. Stop, and DHT returns to its previous level; over the following 6–12 months you gradually lose the hair it was protecting, and loss resumes its natural course. It’s best thought of as ongoing maintenance rather than a course with an end date — an important point to weigh before starting.

Finasteride and minoxidil together

Finasteride and minoxidil work on completely different mechanisms — one lowers DHT, the other extends the growth phase and improves blood supply to the follicle. Used together they consistently outperform either alone, which is why a combined plan is often recommended. If you’ve had, or are planning, a transplant, finasteride also protects your non-transplanted hair, reducing the odds of needing further surgery.

Common questions

Does finasteride regrow hair or just stop loss? Both, for many men — it reliably halts progression and often regrows some, especially at the crown.

How long before I see results? Expect 3–6 months for stabilisation and up to 12 months for the full effect.

Are the side effects permanent? For the large majority, no — they’re uncommon and usually reverse. Persistent effects are rare but reported, which is why a clinician consultation matters.

Can women take it? Not those who are or may become pregnant. Women are usually treated differently — a diagnosis-led plan is the right first step.

Finasteride at the hairline versus the crown

Finasteride’s effect isn’t uniform across the scalp. The strongest, most reliable response is at the crown and mid-scalp, where the evidence for both maintenance and regrowth is clearest. The frontal hairline and temples respond less predictably — finasteride can hold ground there, but it rarely rebuilds a hairline that has already receded significantly. This is why a realistic plan often pairs finasteride (to protect and thicken everything behind the hairline) with a transplant for the frontal zone, rather than expecting one tool to do both jobs.

What about dutasteride?

Dutasteride is a close relative that blocks both type I and type II 5-alpha-reductase, lowering DHT even further than finasteride. Some men who plateau on finasteride are moved to it under specialist supervision. It’s more potent but less widely licensed specifically for hair loss, and the side-effect considerations are similar, so it’s a clinician-led decision rather than a first step.

Separating myth from fact

Finasteride attracts more online myth than almost any medicine. A few worth correcting: it does not lower testosterone (it lowers DHT specifically, and testosterone often rises slightly); it is not a steroid; and the large majority of men take it with no sexual side effects at all. At the same time, the honest counterpoint stands — side effects are real for a minority, which is exactly why it’s prescribed after a proper conversation rather than bought blind. Good decisions come from balanced information, not forum horror stories or marketing gloss.

Monitoring and reviews

Because finasteride is a long-term medicine, it deserves proper follow-up. We review how you’re getting on, track your hair with photographs over time, and check that you’re tolerating it well — adjusting the plan (including switching to topical where appropriate) rather than leaving you to it. That ongoing oversight is part of what separates a clinical plan from an online subscription.

Minoxidil Explained

Can I Take Finasteride and Minoxidil Together?

Should I Start Medication Before or After a Hair Transplant?