Finasteride and Minoxidil Side Effects: What the UK's Own Data Says
Millions of men take hair loss medication every year. Most of them have never seen the actual side effect data. The UK's medicines regulator, the MHRA, publishes it; we pulled it together with clinical trial figures so you can see what the numbers really say.
Updated March 2026 · 10 min read
How Popular Are These Drugs in the UK?
Finasteride and minoxidil are the two most widely used hair loss medications worldwide. In the UK, they sit at opposite ends of the accessibility spectrum.
Finasteriderequires a prescription. At the 1mg dose used for hair loss (branded as Propecia), it's only available privately. The NHS does not prescribe finasteride for pattern hair loss. The 5mg version (Proscar) is available on the NHS, but only for benign prostatic hyperplasia. In the 12 months to March 2024, 4.3 million prescriptions for finasteride 5mg were dispensed in English primary care alone [1]. The MHRA has noted it cannot obtain accurate usage data for the 1mg dose because of its private prescription status [2].
Minoxidil is available over the counter. You can buy it at Boots, Superdrug or any high-street pharmacy without a prescription. It comes as a topical solution, foam or spray (2% and 5% concentrations), and more recently as low-dose oral tablets prescribed off-label by dermatologists.
Finasteride: The MHRA Yellow Card Data
The Yellow Card scheme is the UK's system for reporting suspected side effects of medicines. Anyone can submit a report: patients, pharmacists and doctors. The MHRA published a comprehensive safety review of finasteride in 2024 [2]. Here's what the data shows.
Sexual Dysfunction
Psychiatric Effects
A few things to keep in mind when reading these numbers. Yellow Card reports are voluntary: not every side effect gets reported, so the true figure could be higher. But they also include both the 1mg (hair loss) and 5mg (prostate) doses, and most prescribed finasteride in the UK is the 5mg version. The MHRA itself notes the data cannot prove causation; it shows correlation.
What makes the data noteworthy is the persistence. In almost half the sexual dysfunction reports, the side effect was recorded as "not recovered" or "not resolved" even after stopping finasteride [2]. That's unusual. Most drug side effects clear up once you stop taking the medicine. The MHRA considered this significant enough to mandate a patient alert card in all finasteride packs [3].
The MHRA's advice for men taking 1mg finasteride for hair loss is blunt: if you develop depression or suicidal thoughts, stop taking the drug immediately and contact your doctor [2][3].
How Effective Is Finasteride?
The side effects need context. Finasteride is popular because, for most men, it works. The clinical data is genuinely strong.
| Measure | Result | Source |
|---|---|---|
| Men who maintained or increased hair count (12 months) | 86% | [4] |
| Men who experienced improvement in hair growth | 91.5% | [5] |
| Reduction in visible hair loss risk over 5 years | 93% | [6] |
| Hair count increase after 2 years (vertex) | +16% average | [5] |
| Sexual dysfunction rate in trials (finasteride) | 1.2 – 1.4% | [4] |
| Sexual dysfunction rate in trials (placebo) | 1.0% | [4] |
Those numbers tell a clear story. Finasteride works for the vast majority of men who take it. The controversy isn't about effectiveness; it's about whether the side effect risk, however small in percentage terms, is worth it when the side effects can persist.
The gap between the trial data and the MHRA reports is worth noting too. Trials put sexual dysfunction at 1.2 to 1.4% of users. The MHRA has accumulated 426 reports over 30 years across millions of prescriptions. These numbers aren't contradictory: they suggest that side effects are uncommon but, when they do occur, can be severe enough for people to formally report them.
Minoxidil: Side Effects by Type
Minoxidil has a very different risk profile to finasteride. It doesn't interfere with hormones. Its side effects are mostly localised and mild, particularly in topical form.
Topical Minoxidil
Common side effects
Rare side effects
Oral Minoxidil
Common side effects
Serious (monitored)
The difference between topical and oral minoxidil is significant. Topical application keeps most of the drug on the scalp. Very little gets absorbed into the bloodstream, which is why systemic side effects like heart rate changes are rare with foam or spray.
Oral minoxidil is a different story. It was originally developed in the 1970s as a blood pressure medication; the hair growth was a side effect that got repurposed. Low-dose oral minoxidil (0.25mg to 5mg daily) is increasingly prescribed off-label for hair loss, but it requires monitoring. Patients on oral minoxidil should have their blood pressure and heart rate checked regularly [7].
One practical note: propylene glycol in the liquid solution is often the cause of scalp irritation, not the minoxidil itself. Switching to the foam version, which doesn't contain propylene glycol, often resolves the irritation [8].
How Effective Is Minoxidil?
Minoxidil doesn't work as dramatically as finasteride for most men, but it still has solid clinical backing. And because it doesn't affect hormones, it works for both men and women.
| Measure | Result | Source |
|---|---|---|
| Men with reduced alopecia area (5%, 12 months) | 62% | [9] |
| Men reporting increased density (5%, 4 months) | 74%+ | [10] |
| 5% vs 2% extra regrowth over 48 weeks | 45% more | [11] |
| Average density increase (5%, 12 months) | +18.9 hairs/cm² | [9] |
| Time to first visible results | 3 – 6 months | [9][10] |
| Requires ongoing use | Yes, indefinitely | [9] |
Both finasteride and minoxidil share a critical caveat: if you stop, the benefits reverse. Finasteride's effects tend to fade within 12 months of stopping. Minoxidil is faster; hair loss typically resumes within weeks. This is a lifetime commitment for as long as you want to keep the results.
What the NHS Actually Recommends
The NHS recognises both medications as treatments for pattern hair loss but takes a notably cautious stance [12].
For finasteride: the NHS website lists it as a prescription medication for male pattern baldness, notes its mechanism of reducing DHT levels, and clearly flags the risk of sexual side effects and depression. It states that some side effects can continue even after stopping the medication. The NHS does not prescribe finasteride 1mg for hair loss; it's private-only.
For minoxidil: the NHS lists it as an over-the-counter treatment. It notes that results take 2 to 4 months to appear, that treatment must continue indefinitely to maintain benefits, and that it doesn't work for everyone.
Neither treatment is positioned by the NHS as a first-line recommendation. The NHS hair loss page covers a range of options including wigs, counselling for the psychological impact, and referral to dermatology for conditions like alopecia areata [12]. The tone is pragmatic: these drugs can help, they have side effects, and there are other paths.
Non-Drug Alternatives
If the side effect profile puts you off medication, or if you've tried finasteride and minoxidil without results, several non-pharmaceutical options are available across the UK.
Hair systems are the most immediate solution. A custom-made unit bonded to your scalp gives you a full head of hair the same day, with no drugs and no surgery. Our cost guide covers what you'll pay. Systems need replacing every 3 to 6 months and require maintenance appointments, but there are no systemic side effects.
SMP (scalp micropigmentation) creates the look of a closely shaved head using cosmetic pigment dots. No medication, no ongoing maintenance bar occasional touch-ups every few years. Read our SMP vs hair systems comparison for a detailed breakdown.
PRP therapy (platelet-rich plasma) uses injections of your own concentrated blood plasma into the scalp. Evidence is promising but still developing, and it typically requires multiple sessions at £200 to £500 each.
Low-level laser therapy (LLLT) uses devices like laser caps or combs to stimulate follicles. Clinical evidence is more limited than for medication, but it carries effectively no side effects.
Explore Non-Surgical Options Near You
Browse clinics offering hair systems, SMP, PRP and other non-drug treatments. Filter by location, check reviews and book a free consultation.
Frequently Asked Questions
Can I get finasteride on the NHS?+
Not for hair loss. Finasteride 1mg (Propecia) is only available via private prescription in the UK. You can get it from your GP privately, from online pharmacies or from hair loss clinics. Finasteride 5mg is available on the NHS, but only for treating an enlarged prostate, not hair loss.
How long do finasteride side effects last after stopping?+
For most men, side effects resolve within a few weeks of stopping. But the MHRA data shows that in almost half of the 426 sexual dysfunction reports, the outcome was recorded as "not recovered" or "not resolved" even after stopping the drug. This persistence issue is what prompted the MHRA to issue updated safety warnings.
Is minoxidil safer than finasteride?+
Topical minoxidil has a much milder side effect profile than finasteride. Its most common issues are localised: scalp irritation, dryness and itching. It doesn't affect hormones the way finasteride does. Oral minoxidil carries more risk (cardiovascular effects, fluid retention) and should be prescribed and monitored by a doctor.
Do finasteride side effects happen to everyone?+
No. Clinical trials put the rate of medication-related sexual dysfunction at around 1.2% to 1.4% of users, compared to 1% in the placebo group. So the actual excess risk appears small in trials. But the MHRA Yellow Card reports suggest that when side effects do occur, they can be serious and sometimes persistent.
What non-drug alternatives exist for hair loss?+
Several. Hair systems give you a full head of hair without any medication. SMP (scalp micropigmentation) creates the appearance of a buzz cut. PRP therapy uses your own blood plasma to stimulate growth. Low-level laser therapy is another option, though evidence is more limited. Our directory lists clinics offering all of these across the UK.
Can women use finasteride or minoxidil?+
Women should not use finasteride; it can cause birth defects in male babies and is not licensed for women in the UK. Minoxidil is used by women and is available in 2% and 5% concentrations. The 5% version is generally more effective but carries a higher chance of unwanted facial hair growth.
Sources
Data verified March 2026. MHRA figures as of April 2024 publication.
NHS / Government
- BMJ / OpenPrescribing — finasteride 5mg prescription volumes in England ↗
- MHRA Drug Safety Update — finasteride: risk of psychiatric and sexual side effects ↗
- Pulse Today — MHRA finasteride safety review coverage ↗
- DermNet NZ — finasteride for hair loss: clinical trial data ↗
Clinical Research
- Kaufman et al. — Finasteride in the treatment of men with androgenetic alopecia (PubMed / NIH) ↗
- ResearchGate — 5-year likelihood of visible hair loss progression with finasteride ↗
- Gloucestershire Hospitals NHS Trust — oral minoxidil patient information ↗
- Boots Pharmacy — minoxidil product information and side effects ↗