The Definitive Guide to Dutasteride

Dutasteride is a prescription medicine and one of the most potent treatments available for androgenetic hair loss. It is a close relative of finasteride and works in much the same way, but it suppresses DHT more completely. Dutasteride started out as a prostate medication. Unlike finasteride, it is not licensed for hair loss anywhere in the UK. Despite this, it has uses off-label as a tablet and in topical compounded treatments usually when finasteride has not been enough. This guide explains how dutasteride works and how it compares to finasteride. We review who it is suitable for, the differences between the oral and topical forms, what results to expect and its side effects. Discover the latest regulatory position and how to get it in the UK for hair loss.

What is Dutasteride?

Dutasteride is a 5-alpha-reductase inhibitor. It got approval by the FDA in 2002 as a 0.5mg capsule (Avodart) to treat enlarged prostates. It has never been licensed for hair loss in the UK or the US. However, oral dutasteride 0.5mg has approval for male pattern hair loss in South Korea, Japan and Taiwan.

Like finasteride, dutasteride works by blocking 5-alpha-reductase. This is the enzyme that converts testosterone into DHT, the hormone behind genetic hair loss. We explain this process, and how rising DHT drives follicular miniaturisation, in our finasteride guide. The key difference is that there are two forms of the enzyme, type I and type II. Finasteride blocks only type II. Dutasteride blocks both, and it is more potent at each. This is why it suppresses DHT more completely. At the standard 0.5mg daily dose, dutasteride lowers serum DHT by more than 90%, compared with around 70% for finasteride at 1mg.

What’s the Difference Between Dutasteride vs Finasteride?

Generally speaking, dutasteride is the more potent of the two. That extra potency is its headline advantage, but it is not the only difference, and it is not always an advantage. The practical differences between finasteride vs dutasteride include:

• Half-life: Finasteride clears the body within hours, with a half-life of 6 to 8 hours. Dutasteride has a half-life of around five weeks. This means a missed dose matters far less, because levels stay steady. It also means the drug, and and any side effects, can take months to clear after you stop.
• Effectiveness: Because it suppresses more DHT, dutasteride tends to perform better on hair count in head-to-head trials. A randomised controlled trial found oral dutasteride 0.5mg produced significantly more thick hair than finasteride 1mg over 24 weeks.
• Licensing: This is a key practical difference. Finasteride 1mg is licensed for men with male pattern hair loss in the UK in the form of a prescription only oral medicine. Dutasteride is not licensed for hair loss in the UK at all, so it is only ever used off-label as a tablet or as an unlicensed compounded treatment.
• Side effects: Both share the same side effect profile, which we cover below. The key difference is that dutasteride’s long half-life means any side effects can take longer to settle after stopping.

Despite being more potent, dutasteride is not the default choice. Finasteride is first-line as it has the longest safety record and is enough for most men. Dutasteride is usually reserved for when finasteride has not done enough or has stopped working.

Is Dutasteride Available for Hair Loss in the UK?

Dutasteride is licensed in the UK under the brand name Avodart, and as generic versions, but only to treat an enlarged prostate. It has no UK licence for hair loss. This is a key difference from finasteride, which is licensed for male pattern hair loss at 1mg.

This means that any dutasteride prescribed for hair loss is used outside its licence. There are two ways this is done. The oral capsule is prescribed off-label, meaning a licensed medicine used for an unapproved purpose. The topical form is an unlicensed special, compounded by a pharmacy to order. Both are legal and routine in UK medical practice. If you’re interested, we explain the distinction in our guide to licensed, off-label and unlicensed medicines.

Not having formal approval for hair loss does not make dutasteride unsafe. However, it does mean it should be prescribed by a doctor or medical prescriber after careful assessment of your suitability and will monitor you. This is a prescription only medicine with some potentially serious side effects so you should never use it without proper medical supervision.

What Doses & Concentrations are Used in Hair Loss?

Dosing depends on the form, as well as on dutasteride’s unusually long half-life, which sets it apart from finasteride. Where finasteride clears the body in hours, dutasteride lingers for weeks and this shapes dosing of both the oral and topical forms. Your prescriber will set the right dose and frequency for you, but the general approach for each form is:

• Oral dutasteride: The standard dose is 0.5mg once daily. This is the same dose for treating the prostate and the one you find across the hair loss trials. There is also growing interest in microdosing dutasteride, which means taking lower or less frequent doses than the standard. Because the drug lingers in the body for weeks after each dose, some evidence suggests that taking it just two or three times a week can suppress DHT almost as effectively as daily use. This is not a licensed treatment for hair loss and as such there is no standard dose or frequency for this purpose. However, some doctors may prescribe it off-label on a patient by patient basis and will advise on dose depending on each individual’s needs.
• Topical dutasteride: There is no standard strength so use of topical dutasteride is typically at concentrations ranging from 0.001% to 0.3% with 0.1% to 0.3% being the standard compounding range. Anything below 0.1% counts as a microdose. A small phase II trial found that a 0.05% solution applied daily could match or even outperform oral finasteride on hair growth, with minimal change to serum DHT. Lower concentrations like these are increasingly popular to keep systemic absorption to a minimum whilst maintaining the effect at the scalp. How often you apply it matters as much as the strength. Many clinics, including City Skin Clinic, compound topical dutasteride to suitable patients and often combine it with minoxidil, tretinoin, melatonin or caffeine in a single formula. As with all compound treatments, there’s a balance between concentration and frequency to optimise the effect on the scalp whilst keeping systemic absorption to a minimum.

What Results Can You Expect from Dutasteride?

Dutasteride is one of the most effective hair loss treatments available. That said, the same realistic expectations apply to both, because they work in the same way. Dutasteride protects the hair you have first, and regrows some of what you have lost second. The main things to keep in mind are:

• It works slightly better than finasteride: In a head-to-head trial of 917 men, oral dutasteride 0.5mg produced significantly more hair growth than finasteride 1mg over 24 weeks. In a separate placebo-controlled trial, men on dutasteride gained an average of 12.2 hairs per cm² at six months, compared with 4.7 on placebo.
• Progress is slow: Expect at least 3 to 6 months before you see a meaningful change and up to 12 months for the full effect. A 52-week study found between 76% and 85% of men improved, with the gains at 12 months building on those seen at 6 months.
• Expect a shed first: As with finasteride, some men notice increased shedding in the early weeks. This is usually a sign the hair cycle is resetting rather than a sign of failure.
• The gains are not permanent: If you stop, the benefit fades and your original pattern of loss resumes. Because of dutasteride’s long half-life this happens more slowly than with finasteride but it still happens.

Is Dutasteride Safe for Hair Loss?

Like finasteride, dutasteride is effective and with appropriate use, mostly safe. It shares the same side effects as finasteride, because both work by suppressing DHT. The most serious of these come down to how much DHT suppression occurs throughout the body. If anything, dutasteride’s more complete DHT suppression and its long half-life mean these effects warrant even more caution. The potential side effects of dutasteride include:

• Sexual: Decreased libido, erectile dysfunction and reduced ejaculate volume. In a minority of men these side effects can persist even after stopping.
• Psychological: Depression, anxiety and even suicidal thoughts.
• Breast: Tenderness or enlargement (gynaecomastia). Ensure you investigate any new breast lumps or changes promptly.
• Reproductive: Testicular pain, and reduced fertility or semen quality that tends to improve after stopping.
• Allergic reactions: Including rash, itching and swelling. Avodart capsules also contain a soya derivative. So dutasteride is not suitable for anyone with a soya or peanut allergy.

These side effects can occur with any form of dutasteride. In theory, however, they are less likely with the topical form, because far less of the drug reaches the bloodstream. Topical dutasteride can also cause local side effects where you apply it such as scalp irritation, itching and dryness. These are usually mild and settle as the skin adjusts. There is one important caveat that sets dutasteride apart from finasteride. Its very long half-life means that any side effects, if they do occur, can take considerably longer to settle after stopping, because the drug remains in the body for weeks.

The regulatory position reflects this caution. In 2024, the MHRA introduced patient alert cards and strengthened warnings for finasteride. In 2025, following a European review, it gave a precautionary warning to dutasteride too, noting reports of mood alterations including depression and suicidal thoughts were also possible. Anyone taking dutasteride who develops depression or suicidal thoughts should consult their doctor as soon as possible. The same is also true for sexual side effects. This is one of the reasons dutasteride is a prescription-only medicine that needs proper medical supervision.

What Other Treatments Work Best with Dutasteride?

Whilst dutasteride blocks the hormone that drives pattern hair loss, but it does not stimulate growth directly. This is why it works best alongside treatments that act through other mechanisms, so their benefits add up rather than overlap. The actives most often combined with dutasteride are:

• Minoxidil: This is the best-evidenced partner. It prolongs the growth phase and improves blood flow to the follicle, which is a completely separate mechanism from DHT suppression. The two are often compounded into a single topical treatment.
• Microneedling: This stimulates the follicle through the skin’s healing response and can improve absorption of topical treatments.
• Supportive actives: Ingredients like tretinoin, melatonin and caffeine can support and protect the follicle. They are not usually effective alone and are better together as part of a compounded formula.

Because dutasteride’s benefits depend on continued use, stopping means your hair loss will gradually return. Thanks to its long half-life this happens more slowly than with finasteride, but it still happens over the months that follow. If you are considering stopping, for side effects or any other reason, make it an informed decision and discuss it with your clinician first. Our posts on stopping treatment and alternatives to finasteride and dutasteride cover these options in detail.

Who Can & Cannot Use Dutasteride?

Dutasteride is more potent than finasteride and has no licence for hair loss. This means patient selection matters even more. People who should avoid it, or use it only with caution, include:

• Women: Dutasteride is not suitable for pre-menopausal women. However, like finasteride, some doctors may use it to treat hair loss in some postmenopausal women. For most women though, spironolactone is usually the more common anti-androgen for hair loss.
• Pregancy: Anyone pregnant, breastfeeding or trying to conceive must not take dutasteride or handle the capsules, as it can interfere with the genital development of a male foetus. Because it absorbs through the skin, this applies to the topical form too.
• Anyone with a soya or peanut allergy: Avodart capsules contain a soya derivative and those with allergies should avoid it.
• Men who donate blood: Because dutasteride stays in the body for months, men taking it should not donate blood until at least six months after their last dose. This is to avoid the drug reaching a pregnant transfusion recipient.
• Anyone with a history of depression: Share any mental health history with your prescriber as it is best to avoid this medicine give it’s potential risks.
• Adults only: Dutasteride is not suitable for anyone under the age of 18.

As with any hair loss treatment, it is worth confirming the cause of your hair loss first. Dutasteride only helps DHT-driven loss, so it does nothing for shedding caused by iron deficiency, thyroid problems or a scarring alopecia, which need treating in their own right.

How to Get Dutasteride in the UK

Dutasteride is prescription-only in every form, so you cannot buy it over the counter. Because it is not licensed for hair loss, it is only available off-label or as an unlicensed compounded treatment. It always requires prescription and monitoring by a doctor or medical provider who deems it appropriate for you. It is not available on the NHS for hair loss. Checkout our review of how to access dutasteride for hair loss in the UK if it is appropriate for you.

At City Skin Clinic, we believe hair loss treatment should be personal. We provide compounded hair loss treatments containing topical dutasteride and other actives where appropriate. After an online consultation, one of our doctors will design a bespoke treatment plan for you. Read more about our hair loss treatments for men and women. Start your consultation with one of our doctors today and take the first step towards regrowing your hair.

This article is for general information and does not constitute medical advice. Dutasteride is a prescription-only medicine and you should only use it under the supervision of a medical prescriber. Always read the patient information leaflet and report any suspected side effects to the MHRA via the Yellow Card scheme.