Dutasteride is a prescription 5-alpha reductase inhibitor that reduces scalp DHT by approximately 90%, compared with around 70% for finasteride. It is licensed in the UK for benign prostatic hyperplasia (Avodart) but is increasingly prescribed off-label for male pattern hair loss (androgenetic alopecia) when finasteride alone has not delivered sufficient results. Below, we cover the clinical evidence, how it compares with finasteride, UK prescribing rules, costs, side effects, and what to expect from treatment.
In this article
- What is dutasteride and how does it work?
- Dutasteride vs finasteride: what does the evidence say?
- Key clinical trial results
- Who is dutasteride for?
- Dosage and how to take it
- Side effects and safety
- How to get dutasteride in the UK
- How much does dutasteride cost in the UK?
- Combination therapy: dutasteride with minoxidil
- Topical dutasteride: an emerging option
- Frequently asked questions
What is dutasteride and how does it work?
Male pattern hair loss is driven by dihydrotestosterone (DHT), a hormone produced when the enzyme 5-alpha reductase converts testosterone. DHT binds to receptors in hair follicles, gradually miniaturising them until they stop producing visible hair.
Dutasteride blocks both type 1 and type 2 isoforms of 5-alpha reductase, while finasteride targets mainly type 2. Because it inhibits both enzymes, dutasteride suppresses scalp DHT more aggressively. Studies report scalp DHT reductions of around 90% with dutasteride 0.5 mg daily, compared with approximately 70% for finasteride 1 mg daily.
The drug has a long half-life of approximately five weeks at steady state (compared with around six hours for finasteride), meaning it takes longer to reach full effect but also longer for any side effects to clear after stopping.
Dutasteride vs finasteride: what does the evidence say?
Head-to-head trials consistently show dutasteride outperforming finasteride on hair count and thickness, though both drugs are effective treatments for androgenetic alopecia.
| Feature | Dutasteride 0.5 mg | Finasteride 1 mg |
|---|---|---|
| Enzyme targets | Type 1 and type 2 | Mainly type 2 |
| Scalp DHT reduction | ~90% | ~70% |
| Half-life | ~5 weeks (steady state) | ~6 hours |
| UK hair loss licence | Off-label (licensed for BPH) | Licensed (Propecia) |
| Hair count advantage (meta-analysis) | +28.6 hairs more than finasteride (p < 0.00001) | Baseline comparator |
| Time to results | 3 to 6 months | 3 to 6 months |
| Sexual side-effect rate | Comparable (no significant difference in trials) | ~1.8% in clinical trials |
| UK cost (30 capsules/tablets) | From ~£23 | From ~£14 |
The key clinical takeaway: dutasteride produces a statistically significant improvement in hair count over finasteride, with a comparable side-effect profile. However, finasteride remains the recommended first-line treatment because it is licensed for hair loss in the UK, has a shorter half-life (meaning side effects clear faster if they occur), and costs less.
Key clinical trial results
Three major studies underpin the evidence for dutasteride in hair loss:
| Study | Sample | Duration | Result (hair count change) |
|---|---|---|---|
| Olsen et al. (2006) | Not specified | 24 weeks | Dut 0.5 mg: +95 | Fin 5 mg: +76 | Placebo: -32 |
| Harcha et al. (2014) | 917 men, aged 20 to 50 | 24 weeks | Dut 0.5 mg: +90 | Fin 1 mg: +57 | Placebo: -4.9 |
| Shanshanwal et al. (2017) | Not specified | 24 weeks | Dut 0.5 mg: +23.8 | Fin 1 mg: +4 |
A 2019 meta-analysis pooling three RCTs (576 men) found dutasteride produced a mean increase of 28.57 more hairs than finasteride (95% CI: 18.75 to 38.39, p < 0.00001). Investigator assessments of both vertex and frontal improvement also favoured dutasteride significantly.
A 2024 systematic review of nine studies (Nagshabandi et al., Dermatology Reports) confirmed these findings, reporting that dutasteride 0.5 mg was significantly more effective than finasteride 1 mg across multiple endpoints. However, the authors noted that most evidence comes from short-term studies in men, and high-quality data in women remains limited.
Who is dutasteride for?
Dutasteride is typically considered for men with androgenetic alopecia who meet one or more of these criteria:
- Inadequate response to finasteride: the most common reason. If 12 months on finasteride 1 mg has not slowed hair loss sufficiently, a prescriber may switch to dutasteride
- Moderate to advanced hair loss: Norwood stages III to V, where more aggressive DHT suppression may be needed
- Preference for stronger DHT reduction: some men choose dutasteride first, though prescribers generally recommend trying finasteride initially because of its shorter half-life and established safety profile
Dutasteride is not suitable for women, children, or anyone who is pregnant or may become pregnant. It can be absorbed through the skin and may cause birth defects in a male foetus. Men taking dutasteride should not donate blood for at least six months after their last dose.
Dosage and how to take it
The standard dose for hair loss is 0.5 mg once daily, taken orally with or without food. Capsules should be swallowed whole (not opened or crushed, as the contents can irritate the mouth and throat).
Key points about timing and expectations:
- Onset: most men notice reduced shedding within 1 to 3 months, with visible improvement from 3 to 6 months
- Full effect: may take 12 to 24 months to see the maximum benefit
- Shedding phase: some men experience temporary increased shedding in the first few weeks as weakened hairs are replaced by healthier ones. This is normal and usually resolves within a few months
- Continuous use: benefits are maintained only while taking the drug. Hair loss will resume gradually after stopping, though the long half-life means the effect tapers slowly over several months
Side effects and safety
The side-effect profile of dutasteride is comparable to finasteride. A meta-analysis of three RCTs found no statistically significant difference between the two drugs for altered libido (OR 1.12, p = 0.54), erectile dysfunction (OR 1.18, p = 0.70), or ejaculation disorders (OR 0.75, p = 0.58).
Common side effects (affecting a small percentage of users) include:
- Decreased libido
- Erectile difficulty
- Ejaculation changes (reduced volume)
- Breast tenderness or enlargement (gynecomastia)
- Mood changes
In long-term BPH trials, sexual side-effect rates fell from 6.0% in year one to 0.4% by year four, suggesting the body adapts over time for most men.
Because dutasteride has a much longer half-life than finasteride (weeks versus hours), any side effects that do occur may take longer to resolve after stopping the drug. This is a key consideration when choosing between the two treatments.
Prostate cancer screening: dutasteride can halve PSA (prostate-specific antigen) levels, which may mask elevated readings. Inform your GP and any healthcare professional conducting a PSA test that you are taking dutasteride so they can adjust the interpretation.
How to get dutasteride in the UK
Dutasteride is a prescription-only medicine (POM) in the UK. It is licensed under the brand name Avodart for benign prostatic hyperplasia, but prescribers may issue it off-label for androgenetic alopecia after a clinical consultation.
There are two main routes to obtaining a prescription:
- Your GP: some GPs will prescribe dutasteride off-label for hair loss, particularly if you have already tried finasteride. Others may refer you to a dermatologist. NHS prescriptions are possible but uncommon for hair loss, as most GPs view it as a cosmetic concern
- Online pharmacies and clinics: several UK-regulated online pharmacies (registered with the GPhC) offer dutasteride after an online consultation. A prescriber reviews your medical history and, if appropriate, issues a private prescription. Prices typically range from £15 to £25 per month for generic dutasteride 0.5 mg capsules
When using an online pharmacy, check that it is registered with the General Pharmaceutical Council (GPhC) and displays the Distance Selling logo.
How much does dutasteride cost in the UK?
| Supply | Generic dutasteride 0.5 mg | Avodart (brand) |
|---|---|---|
| 1 month (30 capsules) | From ~£23 | From ~£43 |
| 3 months (90 capsules) | From ~£54 | From ~£120 |
| 6 months (180 capsules) | From ~£93 | From ~£240 |
For comparison, generic finasteride 1 mg costs from approximately £14 per month in the UK, making it the more affordable first-line option. Prices vary between pharmacies and may be lower with multi-month subscriptions.
Combination therapy: dutasteride with minoxidil
Many dermatologists recommend combining a 5-alpha reductase inhibitor with topical minoxidil for maximum effect. While dutasteride reduces DHT production, minoxidil works through a separate mechanism: it increases blood flow to the follicle and extends the growth (anagen) phase of the hair cycle.
The two treatments are complementary rather than overlapping. Combining dutasteride 0.5 mg daily with minoxidil 5% solution applied twice daily addresses hair loss from two directions and may produce results that neither drug achieves alone. Your prescriber can advise whether combination therapy is appropriate for your stage of hair loss.
For a detailed guide to minoxidil, including formulations, application techniques, and timelines, see our Complete Guide to Minoxidil for Hair Loss in the UK (coming soon).
Topical dutasteride: an emerging option
Research is exploring whether topical (scalp-applied) dutasteride can deliver the drug's benefits while reducing systemic exposure and the risk of sexual side effects.
A 2025 phase II study (Panuganti et al.) found that topical dutasteride reduced scalp DHT levels while producing a smaller drop in blood DHT than oral dosing. This suggests topical formulations may offer a better balance of effectiveness and tolerability.
However, topical dutasteride is not yet widely available in the UK. Some compounding pharmacies prepare bespoke topical solutions, typically at concentrations of 0.01% to 0.05%, but these are not standardised products and are not covered by the same regulatory framework as licensed medicines. If you are interested in topical dutasteride, discuss it with a dermatologist who can advise on appropriate formulations and monitoring.
When to see a dermatologist
Consider seeking specialist advice if:
- Finasteride has not slowed your hair loss after 12 months
- You are experiencing rapid or diffuse hair loss (which may indicate a condition other than androgenetic alopecia)
- You want to discuss combination therapy or topical options
- You are a woman experiencing hair thinning (dutasteride is not suitable, but other treatments exist)
A dermatologist can perform a detailed scalp examination, often using a dermatoscope to assess follicle miniaturisation, and recommend a treatment plan tailored to your pattern and severity of hair loss.
Frequently asked questions
Is dutasteride better than finasteride for hair loss?
Clinical trials show dutasteride produces greater hair regrowth than finasteride, with a meta-analysis reporting an average of 28.6 more hairs per cm² (p < 0.00001). However, finasteride remains the recommended first-line treatment in the UK because it is licensed for hair loss, has a shorter half-life, and costs less. Dutasteride is typically reserved for men who have not responded adequately to finasteride.
Can I get dutasteride on the NHS for hair loss?
It is possible but uncommon. Most GPs consider hair loss a cosmetic concern and will not prescribe dutasteride on the NHS for it. You can request a private prescription from your GP or obtain one through a GPhC-registered online pharmacy after an online consultation. The cost is typically £15 to £25 per month for generic capsules.
How long does dutasteride take to work for hair loss?
Most men notice reduced shedding within one to three months. Visible improvement in hair density and thickness typically becomes apparent after three to six months, with the full effect taking 12 to 24 months. Some men experience temporary increased shedding in the first few weeks, which is a normal part of the treatment process.
What are the side effects of dutasteride?
The most commonly reported side effects are decreased libido, erectile difficulty, and ejaculation changes. A meta-analysis found no statistically significant difference in these side effects between dutasteride and finasteride. In long-term studies, sexual side-effect rates fell from 6% in year one to under 1% by year four. Breast tenderness and mood changes can also occur. Because dutasteride has a long half-life (approximately five weeks), side effects may take longer to clear after stopping compared with finasteride.
Can I switch from finasteride to dutasteride?
Yes. Many men switch after an inadequate response to finasteride. Your prescriber may recommend stopping finasteride and starting dutasteride the next day, or tapering one while introducing the other. The two drugs should not be taken simultaneously, as this increases side-effect risk without clear additional benefit. Allow at least six months on dutasteride before judging whether the switch has been worthwhile.
Is dutasteride safe long-term?
Long-term safety data comes primarily from BPH trials lasting up to four years, which showed that sexual side effects decreased over time. No increased risk of prostate cancer incidence was found, although a cancer detected while on dutasteride may be more likely to be higher grade. As with any long-term medication, regular check-ups with your prescriber are recommended, including PSA monitoring with adjusted reference ranges.
Related guides from the Vena Cava blog
- Finasteride for Hair Loss UK: Everything You Need to Know
- Complete Guide to Minoxidil for Hair Loss in the UK (coming soon)
- Evidence-Based Hair Growth Products UK: 15 Treatments Ranked
- Dermatoscope Buying Guide UK
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Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Dutasteride is a prescription-only medicine. Always consult a qualified healthcare professional before starting, stopping, or changing any medication. If you experience side effects, contact your prescriber or call NHS 111.
