Dutasteride vs Finasteride for Hair Loss: What's the Difference in the UK?

Medically reviewed by Dr Saira Bano, BMBS, BMedSci, MRCGP, PGCert MedEd, SCOPE-Certified Obesity Specialist

If you have been researching hair loss treatment, you have probably come across dutasteride described online as the "stronger" option compared with finasteride. It is a claim that comes up often, and it leaves a lot of men wondering whether it is actually true, and whether they can get hold of it.

This article compares the two medicines clearly: how they work, what the evidence shows, how their side effects compare, and the difference in their UK licensing, which turns out to be one of the most important parts of the picture.

How do dutasteride and finasteride work?

Both medicines belong to the same class, known as 5-alpha reductase inhibitors, and both target the same underlying cause of male pattern hair loss.

That cause is a hormone called dihydrotestosterone, usually shortened to DHT. Your body makes DHT from testosterone using an enzyme called 5-alpha reductase. In men who are genetically susceptible, DHT gradually shrinks the hair follicles on the scalp in a process known as miniaturisation, so hairs grow back progressively thinner and shorter until the follicle stops producing visible hair altogether. [1]

Both medicines work by blocking that enzyme, which lowers DHT levels and slows or halts the process.

The key mechanistic difference is which version of the enzyme each one blocks. There are two main types, type I and type II. Finasteride mainly blocks type II. [1] Dutasteride blocks both type I and type II, which is why it lowers DHT further. [2]

It is worth being careful with the assumption that follows from this. Lowering DHT more does not automatically translate into a better outcome for every individual, and response to either medicine varies considerably from person to person.

Which is licensed for hair loss in the UK?

This is where the two medicines genuinely diverge, and it matters more than any comparison of strength.

Finasteride 1mg is licensed in the UK for the treatment of male pattern hair loss in men, to increase hair growth and prevent further hair loss. [1] It is the established, licensed option, and finasteride is what most men in the UK will be offered for this purpose.

Dutasteride is a different matter. In the UK it is licensed for benign prostatic hyperplasia, an enlarged prostate, and not for hair loss. [2] Using it to treat hair loss in the UK is therefore off-label.

Off-label prescribing means a prescriber can, in certain circumstances, prescribe a medicine outside its licensed use where they judge it appropriate for that individual, taking full clinical responsibility for the decision. It is not the standard route, and it is not a first-line option. It is a clinical judgement made case by case rather than something a patient can select.

One reason readers encounter dutasteride discussed as a hair loss treatment is that it is licensed for exactly that purpose in some other countries, including South Korea and Japan. That does not change its UK status, and content written for other markets can be misleading if you read it as applying here.

What does the evidence say about effectiveness?

Both medicines have been shown in clinical studies to slow hair loss and, for many men, to increase hair count over 6 to 12 months and beyond.

Head-to-head research has generally found that dutasteride produces a somewhat greater increase in hair count than finasteride, which is consistent with it lowering DHT further. In a randomised trial comparing dutasteride 0.5mg, finasteride 1mg and placebo in men with androgenetic alopecia, dutasteride significantly increased hair count and hair width at 24 weeks compared with both finasteride and placebo. [3] That study ran for 24 weeks, which the authors noted as a limitation.

The picture is not entirely one-sided, though. A smaller, more recent randomised trial of 46 men comparing the two in men with moderate to severe androgenetic alopecia found comparable improvement in hair growth between the groups over 24 weeks, with no significant difference on trichoscopic or photographic assessment. [4] Findings at group level also say little about how any particular individual will respond.

Finasteride has the longer track record specifically in hair loss, and a larger body of long-term safety data at the 1mg dose. A good response to finasteride is common, and many men never need to consider anything else.

A few realities apply to both medicines equally:

• Neither restores hair in areas where follicles have been lost for a long time. Both work best on thinning hair rather than completely bald areas.
• Results take time, typically several months before any change is noticeable.
• Shedding can temporarily increase in the first few weeks, which is a recognised part of the process rather than a sign of failure.
• Stopping either medicine leads to the gradual return of hair loss over the following months.

What are the side effects, and how do they compare?

Because both medicines work in the same way, they share a broadly similar side effect profile.

The most commonly reported effects are sexual: reduced sex drive, erectile difficulties and reduced ejaculate volume, along with breast tenderness or enlargement. [1][2] These affect a minority of men, and for many they settle with continued use or resolve after stopping.

In May 2026 the MHRA strengthened its safety warnings for finasteride, confirming an association with sexual dysfunction and with psychiatric effects including low mood, depression and suicidal thoughts, some of which may persist after treatment is stopped. [5] Evidence for dutasteride is very limited, so the MHRA has added a precautionary warning to dutasteride noting that mood changes have been reported with finasteride, a medicine in the same class. [5] Mood changes are something to be aware of and to report. If you take finasteride 1mg and develop depression or suicidal thoughts, stop taking it and contact your doctor as soon as possible. If you take dutasteride and notice these symptoms, contact your doctor promptly. [5]

There is one meaningful difference between the two worth understanding. Dutasteride lowers DHT further and stays in the body far longer, with a half-life measured in weeks rather than the hours that applies to finasteride. [1][2] That means if side effects do occur, they may be more persistent after stopping and are harder to reverse quickly. It is one of the reasons prescribers approach dutasteride more cautiously.

Two precautions apply to both. Both medicines can lower prostate-specific antigen (PSA) test results, so any clinician interpreting a PSA test needs to know you are taking one. [1][2] Women who are pregnant or may become pregnant should not handle crushed or broken finasteride tablets or leaking dutasteride capsules because of the potential risk to a male foetus.

Both are prescription-only medicines requiring clinical assessment, and any side effects should be discussed with your prescriber rather than managed alone.

Which one is right for you?

For most men in the UK, finasteride is the appropriate starting point. It is licensed for hair loss, well studied at the 1mg dose, and effective for a good proportion of men who take it.

Dutasteride may be discussed by a prescriber in specific circumstances, for example where a man has had a genuinely inadequate response to finasteride after a sustained trial at an adequate duration. That is a clinical decision made on an individual basis, weighing the off-label status and the longer persistence of any side effects. It is not something to self-select or to request on the basis of online comparisons.

It is also worth knowing that finasteride is often combined with topical minoxidil, and that this combination is a common and well-supported approach that many men find works well before any question of changing medicine arises.

How SwiftDoctor can help with hair loss

SwiftDoctor's clinicians assess suitability for licensed hair loss treatment through a straightforward online consultation, with discreet delivery and ongoing support throughout treatment. Our male hair loss treatments are prescribed only after a qualified clinician has reviewed your medical history and confirmed the treatment is appropriate for you.

Frequently asked questions

Can you take dutasteride and finasteride together?

No. Both work on the same enzyme, so taking them together is not expected to add benefit and could increase the likelihood of side effects. They are not intended to be combined, and combining them is not a recommended approach.

Can you switch from finasteride to dutasteride?

Switching is a clinical decision rather than a patient one, and in the UK it means moving from a licensed treatment to an off-label one. A prescriber would normally want to see a genuinely inadequate response to finasteride over a sustained period first, and would discuss the off-label status and the longer persistence of any side effects before considering it.

Is topical finasteride or dutasteride available?

Topical formulations of both have been studied and are available from some providers, though in the UK topical versions are generally unlicensed for hair loss. Oral finasteride 1mg remains the licensed option, and any topical alternative should be discussed with a prescriber who can explain its regulatory status.

Does finasteride or dutasteride affect testosterone levels?

Neither lowers testosterone. Both block the conversion of testosterone into DHT, which means testosterone itself is not reduced and may rise slightly. The effects some men notice are related to lower DHT rather than to low testosterone.

Can women take finasteride or dutasteride for hair loss?

Neither is licensed for hair loss in women in the UK, and both are contraindicated in women who are pregnant or may become pregnant because of the risk to the development of a male baby. [1][2] Women experiencing hair loss should speak to a clinician about options appropriate for them rather than using either medicine.

How long do side effects last after stopping?

For many men, side effects settle after stopping finasteride, which clears the body quickly. Dutasteride takes considerably longer to clear, so effects can take months to settle. The MHRA notes that some sexual side effects of finasteride may persist after treatment is stopped, which is why any side effect should be discussed with your prescriber promptly. [5]

Sources

1. Electronic Medicines Compendium (eMC), "Propecia 1 mg Film-Coated Tablets: Summary of Product Characteristics" (Organon Pharma UK), medicines.org.uk
2. Electronic Medicines Compendium (eMC), "Avodart 0.5mg soft capsules: Summary of Product Characteristics" (GlaxoSmithKline UK), medicines.org.uk
3. Gubelin Harcha, W. et al. (2014). Journal of the American Academy of Dermatology, "A randomized, active- and placebo-controlled study of the efficacy and safety of different doses of dutasteride versus placebo and finasteride in the treatment of male subjects with androgenetic alopecia", sciencedirect.com
4. Poostiyan, N. et al. (2026). Journal of Dermatological Treatment, "Efficacy and safety of oral finasteride versus dutasteride in moderate-to-severe androgenetic alopecia in males based on trichoscopic and laboratory findings: a clinical comparison in Iran", tandfonline.com
5. Medicines and Healthcare products Regulatory Agency (MHRA), "Finasteride and dutasteride: updated safety warnings for psychiatric side effects and sexual dysfunction", gov.uk