Finasteride for Hair Loss: How It Works, Who It Is For, and What to Expect

Finasteride is the most researched hair loss medicine on the market and the most prescribed oral treatment for male pattern hair loss in the UK. It is MHRA licensed for use in men aged 18 to 41 at 1mg daily under the brand name Propecia and several generic equivalents (Accord, Aristo, Teva). This guide covers every UK brand you might be dispensed, the licensed and off-label uses, the clinical evidence behind the drug, real side effect rates, cost comparisons, and how finasteride sits alongside dutasteride and topical alternatives.

Finasteride brands available in the UK

Every UK finasteride 1mg tablet contains the same active ingredient at the same dose. What differs is the manufacturer, the tablet appearance and the price. Any UK prescriber will confirm these are clinically interchangeable.

• Propecia (Merck): the original branded finasteride 1mg. The first finasteride licensed for hair loss (MHRA 1998, FDA 1997). Now typically the most expensive option per tablet, often £35 to £60 for 28 tablets at UK retail. Same active as every generic below.
• Finasteride Accord 1mg (Accord Healthcare): a UK generic manufactured by Accord, one of the most commonly dispensed brands in NHS pharmacies. Same 1mg dose, similar oval film-coated tablet. See our Accord Finasteride 1mg product page for pricing.
• Finasteride Aristo 1mg (Aristo Pharma): German-based generic manufacturer, MHRA licensed for the UK. Same 1mg dose.
• Finasteride Teva 1mg (Teva UK): another common UK generic option, dispensed against prescription across UK pharmacies.
• Generic finasteride 1mg (mixed manufacturers): UK pharmacies routinely dispense whichever generic is in stock, all MHRA licensed and clinically equivalent. Our generic Finasteride 1mg starts at £15 for a monthly 28 tablet pack, falling to 36p per tablet on a 12 month value pack.
• Finasteride 5mg tablets (multiple UK generics): MHRA licensed for benign prostatic hyperplasia (BPH), NOT for hair loss. Prescribed off-label for hair loss when split into thirds to give a ~1.67mg daily dose. Cheapest option per month at ~£10 to £14 on our 4 and 12 month packs. See our Finasteride 5mg tablets.

How finasteride works for hair loss

Finasteride is a Type II 5-alpha reductase inhibitor. In plain English: the enzyme 5-alpha reductase converts testosterone into dihydrotestosterone (DHT) inside your body. DHT is the hormone that shrinks (miniaturises) hair follicles in men with a genetic predisposition to male pattern hair loss. Less DHT means less follicle miniaturisation, which means existing follicles stay productive longer and some previously miniaturised follicles can recover.

Key numbers on the mechanism:

• Finasteride 1mg daily reduces serum DHT by roughly 70 percent. Scalp DHT falls in parallel.
• Effect on serum testosterone is minimal, typically a small increase within normal reference range.
• Peak DHT suppression is reached within 24 hours of the first tablet. Sustained daily dosing keeps DHT suppressed.
• DHT levels start returning to baseline within 24 to 48 hours of stopping. Any hair gained is lost over 6 to 12 months once treatment is discontinued.

This is why finasteride is a maintenance treatment, not a course. Gains persist only while treatment continues.

Licensed vs off-label uses in the UK

Finasteride has two MHRA licensed uses in the UK, at two different strengths:

• 1mg daily (Propecia and generics) is MHRA licensed for the treatment of male pattern hair loss in men aged 18 to 41. This is the on-label use for hair.
• 5mg daily (Proscar and generics) is MHRA licensed for benign prostatic hyperplasia (BPH) in older men. This is NOT a licensed hair loss dose.

Off-label uses commonly prescribed by UK prescribers:

• Finasteride 5mg split into thirds for hair loss. Because the dose-response curve for scalp DHT suppression plateaus around 1mg (see clinical evidence below), a split 5mg tablet giving ~1.67mg daily produces similar hair growth outcomes at roughly one-third the monthly cost. UK prescribers routinely accept this off-label approach for cost-conscious patients.
• Finasteride for women over 45 or post-menopausal women under specialist supervision. Not the standard first-line female treatment (spironolactone or topical minoxidil is), but sometimes used when other options have failed.
• Topical finasteride (compounded solution applied to the scalp). MHRA has never licensed a topical finasteride product, so all topical finasteride in the UK is prescribed off-label as a Special (a compounded medicine prepared to individual prescription). See our FINASOL topical finasteride.

Off-label prescribing is legal and common practice in the UK when a prescriber judges it appropriate for the individual patient.

Clinical evidence: the trials behind finasteride

Finasteride has 25+ years of clinical evidence at doses relevant to hair loss. The trials that matter:

• Original Merck 5 year trials (Kaufman et al 1998, published in the Journal of the American Academy of Dermatology): 1,879 men with male pattern hair loss randomised to finasteride 1mg or placebo. At 2 years: 66 percent of treated men had increased hair count versus 7 percent on placebo, and 83 percent maintained or improved vs 28 percent on placebo. Effect sustained at 5 years. This is the trial that supported the MHRA 1998 licence.
• Roberts et al 1999 dose-response study: compared finasteride 0.2mg, 1mg, 5mg and placebo daily in men with androgenetic alopecia over 12 months. The 1mg and 5mg doses produced clinically similar hair count improvements, both significantly better than 0.2mg and placebo. This is the foundation for the split-dose 5mg approach: higher doses do not out-perform 1mg for hair.
• Rossi et al 2011 long term follow up (10 years): Italian cohort of 118 men on finasteride 1mg daily. 86 percent had clinical improvement or stabilisation at 10 years. Adverse events at 10 years were similar to placebo comparator groups. This is the strongest published evidence that finasteride works over the long haul, not just the initial 1 to 2 years.
• Sato et al 2012 meta-analysis: pooled 12 randomised trials of finasteride 1mg in men, confirming ~9 to 10 percent increase in hair count at 1 year and ~15 to 18 percent at 2 years. These are the numbers you see quoted in most hair loss content.

Practical takeaway: finasteride is the most rigorously evidenced oral hair loss treatment. Response rates are high but not universal (roughly 15 percent of men are true non-responders at 1 year). If finasteride 1mg has not moved the needle at 12 months, the next options are dutasteride 0.5mg (stronger DHT block) or combination with minoxidil.

How long does finasteride take to work?

Finasteride is not a short course. It takes months for follicles to respond and the growth cycle to shift towards fewer miniaturised hairs. Expected timeline:

• Weeks 1 to 4: no visible change. Serum DHT is falling by 70 percent but hair does not respond in real time.
• Months 3 to 6: reduced shedding is the first visible sign. You may notice fewer hairs in the shower drain or on your pillow. Visible thickness gains are still weeks away.
• Months 6 to 12: first visible hair count improvements. Full thickness gains are typically judged at 12 months of consistent daily use.
• Months 12 to 24: continued gradual improvement. Peak effect is usually reached at 2 years.
• Years 2 to 10: maintenance. Gains slowly plateau but consistent daily use maintains them.

Missing occasional days: fine, resume the next day. Missing multiple days per week: your DHT suppression is not sustained and you will underperform the trial results. Consistency is more important than the specific time of day.

Side effects: the honest picture

Finasteride is generally well tolerated in the trial data. The published side effects, in order of frequency:

• Sexual side effects (reduced libido, erectile dysfunction, ejaculation disorders): reported by 2 to 4 percent of men on 1mg daily in the original Merck trials, versus roughly 1 to 2 percent on placebo. Reports are usually mild and reversible on stopping the medicine. Some men who report side effects find they resolve while continuing treatment.
• Breast tenderness or enlargement (gynecomastia): rare, roughly 0.5 percent incidence. Usually resolves on stopping.
• Mood changes (low mood, depression, anxiety): reported in post-marketing surveillance but low frequency in trials. Take seriously if it develops; discuss with prescriber.
• Testicular pain: rare.
• Allergic reactions: uncommon rash, pruritus.

On post-finasteride syndrome (PFS): a small subset of men report persistent sexual, mood or physical side effects that continue after finasteride has been discontinued. The published incidence is very low and the mechanism is not fully understood. UK prescribers acknowledge PFS as a real (though uncommon) concern. If you develop side effects on finasteride, tell your prescriber immediately rather than waiting; early discontinuation is associated with better resolution outcomes. If you are worried about PFS specifically before starting, topical finasteride (lower systemic exposure, roughly one-third the sexual side effect rate in Piraccini et al 2022) is a lower-risk alternative.

Finasteride vs the alternatives

UK men researching hair loss treatment have a limited but effective set of options. Here is where finasteride fits:

• Finasteride 1mg oral (this guide): the MHRA licensed first-line oral treatment for male pattern hair loss. Reduces serum DHT by ~70 percent. Roughly £15 to £22 per month at UK generic prices.
• Dutasteride 0.5mg oral: stronger DHT blocker (both Type I and Type II 5-alpha reductase, ~90 to 98 percent DHT reduction). Off-label for hair loss in the UK. Better hair count outcomes in head-to-head trials, but a longer half-life (5 weeks vs finasteride 6-8 hours) means side effects take longer to resolve on stopping. See our Dutasteride 0.5mg. See also our full finasteride vs dutasteride comparison.
• Topical finasteride (FINASOL): the same finasteride active applied to the scalp rather than swallowed, in a 100ml TrichoSol® bottle. Roughly one-third the sexual side effect rate of oral finasteride at similar hair count outcomes (Piraccini et al 2022). Off-label in the UK. See our FINASOL topical finasteride or the full topical vs oral finasteride comparison.
• Minoxidil (topical 2 to 15 percent or oral 2.5 to 5mg): a different mechanism (potassium channel opener, extends anagen phase, growth stimulator). Works alongside finasteride, not instead of it. The classic evidence-backed male regimen is oral finasteride 1mg plus topical minoxidil 5 percent. See our Topical Minoxidil or oral minoxidil 5mg.
• OTC "hair growth" supplements (biotin, saw palmetto, DHT-blocker herbal blends): weak to no evidence. No published RCT shows biotin or saw palmetto matches finasteride 1mg for hair count. Save your money.

What NOT to combine: never take finasteride and dutasteride together (two DHT blockers, no meaningful additional benefit, higher side effect risk). Never take oral finasteride with topical finasteride (same drug, two routes, stacks the dose). Minoxidil with finasteride is fine and encouraged; these are different drugs with different mechanisms.

Dosage

The MHRA licensed hair loss dose is 1mg per day, once daily, at any consistent time. With or without food. Two minutes of effort per day.

A cheaper off-label approach: buy the 5mg tablets and split them into thirds, taking one-third of a tablet daily (roughly 1.67mg). The clinical trial evidence (Roberts 1999) shows this produces similar hair growth to daily 1mg. Cost per month is roughly one-third of the 1mg tablet price. Speak to your prescriber about the split-dose approach if cost is a factor.

Higher doses (2mg, 5mg, 10mg daily) do NOT produce faster or better hair growth. The dose-response plateau is around 1mg for scalp DHT suppression, so taking more just increases side effect risk with no additional benefit.

Storage and shelf life

• Store at room temperature (below 25°C), away from direct sunlight and moisture.
• Keep tablets in their original blister pack or bottle until you take them. The blister foil protects the tablet from moisture and light.
• Sealed pack expiry is on the label (typically 24 to 36 months from manufacture). Do not use after the printed expiry date.
• If splitting 5mg tablets, store the split pieces in the original bottle with the cap closed. Use split tablets within 2 weeks; the cut edge can oxidise if left exposed to air.
• Keep out of reach of children, pets, and anyone pregnant or planning pregnancy. Broken tablets can transfer finasteride through the skin, and finasteride is contraindicated during pregnancy.

Excipients: what is in a finasteride 1mg tablet

Active ingredient: finasteride 1mg. Typical excipients in UK generic finasteride 1mg tablets:

• Lactose monohydrate as the primary filler. If you are severely lactose intolerant, ask your prescriber about lactose-free brands.
• Microcrystalline cellulose, pregelatinised starch, sodium starch glycolate, magnesium stearate as tablet binders, disintegrants and lubricants.
• Docusate sodium as a wetting agent.
• Talc, hypromellose, titanium dioxide and yellow / brown iron oxides in the film coating.

The full excipient list is on the manufacturer Patient Information Leaflet enclosed with your medicine. Different brands (Accord, Aristo, Teva, Milpharm, generic) use slightly different excipient combinations; the active is identical.

Regulatory status: POM, MHRA licensed since 1998

• Finasteride is a prescription only medicine (POM) in the UK at every strength. There is no over the counter finasteride.
• Propecia (finasteride 1mg) has been MHRA licensed for male pattern hair loss since 1998. Generic finasteride 1mg tablets are MHRA licensed to the same clinical file.
• Proscar (finasteride 5mg) has been MHRA licensed for BPH since 1994. The 5mg strength is NOT licensed for hair loss; the split-dose approach is off-label prescribing.
• Free UK prescriber review at checkout: the online medical questionnaire is reviewed by a UK GPhC registered prescriber before dispensing. This assesses eligibility, PFS history, and contraindications.
• Dispensed by a GPhC registered UK partner pharmacy. Every pack we sell is prepared and shipped in the UK.

Patient Information Leaflets and further reading

• Propecia 1mg PIL (medicines.org.uk): the branded manufacturer patient information leaflet.
• NHS: Finasteride: NHS patient information page.
• NICE CKS: Hair loss (androgenetic, male and female pattern): UK clinical summary for prescribers.

Every pack we dispense ships with the manufacturer PIL enclosed. Always read the leaflet supplied with your medicine, and contact your prescriber or the pharmacy if anything is unclear.

Our Finasteride Treatments

Next steps

For the broader UK landscape and how finasteride fits with topical and combination approaches, see our complete UK hair loss treatment guide. Comparing finasteride against dutasteride, the alternative anti-androgen? Read our finasteride vs dutasteride comparison. Considering topical over oral for side effect reasons? See our topical vs oral finasteride guide.