The Definitive Guide to Finasteride

Finasteride is a prescription medicine and one of the most effective treatments available for androgenetic hair loss. It is also the only oral medicine licensed for hair loss in the UK. Finasteride started out as a prostate medication. Doctors then noticed it regrew hair, and it became a first-line treatment for pattern hair loss in men. Whilst its licensed for use as an oral tablet, it is also increasingly used in topical compounded treatments that you apply to the scalp. This guide explains how finasteride works and who it is suitable for. We review the key differences between the oral and topical forms, what results to expect and explore its side effects. Discover the latest regulatory updates and how to get it in the UK for hair loss.

What is Finasteride?

Finasteride is a 5-alpha-reductase inhibitor. It was first approved in 1992 by the FDA as a 5mg tablet (Proscar) to treat enlarged prostates. Later, in 1997, Finasteride 1mg (as Propecia) tablets got approval by the FDA for treating pattern hair loss in men. It is one of only a handful of hair loss treatments with decades of strong evidence behind it.

The way finasteride works is by blocking 5-alpha-reductase. This is the enzyme that converts testosterone into dihydrotestosterone (DHT). DHT is the main hormone behind genetic hair loss. In people who are susceptible to it, DHT binds to receptors in the scalp’s hair follicles and gradually shrinks them. Each growth cycle then produces a finer, shorter and weaker hair, until the follicle eventually stops producing visible hair at all. This process is follicular miniaturisation and it is what drives the receding hairline and thinning crown. By lowering DHT, finasteride slows this miniaturisation, which is why it is one of the most effective DHT blockers we have. At the standard 1mg dose, oral finasteride reduces DHT in the scalp by around 64% and in the blood by about 71%.

What Does Finasteride Treat?

The way finasteride works is critical for understanding what it can and cannot do. Finasteride is only useful for reducing DHT level as this is what drives androgen-related hair loss. This means that finasteride protects more than it restores. Its main job is to stop further loss, with regrowth a welcome bonus rather than a guarantee. Finasteride also only works whilst you use it. This is because DHT climbs back once treatment stops and the original pattern of loss returns over the following 6 to 12 months. As such, finasteride is a long-term treatment rather than a quick fix. Based on available evidence, the main uses of finasteride for hair loss are:

• Male pattern hair loss: This is the main use and where the evidence is strongest. Finasteride is a first-line treatment for male pattern baldness, slowing shedding and regrowing hair, particularly at the crown. It works best when started early, whilst there are still follicles worth saving.
• Female pattern hair loss (limited): Finasteride sometimes has off-label use for some postmenopausal women with female pattern hair loss, with important restrictions we cover below. However, for women and particularly pre-menopausal ones, spironolactone is more commonly for hair loss.
• Receding hairlines & thinning crowns: Finasteride works best at the crown and mid-scalp, which respond more reliably than the frontal hairline. It is more useful in the earlier thinning, miniaturising stages of male pattern hair loss rather than areas that are already fully bald. This is because at this stage there is no live follicle remaining to rescue.

At City Skin Clinic, we use topical finasteride sometimes compounded treatments with other actives where appropriate as part of our hair loss treatments for men and in occasionally for post-menopausal women.

What’s the Difference Between Oral vs Topical Finasteride?

Both forms block the same enzyme and treat the same problem. The difference is that drug delivery affects how much of it ends up circulating around the rest of the body. This is crucial as it determines effectiveness and side effect profile. The main forms of finasteride are:

• Oral finasteride: This is the original and licensed form. It is available by prescription only and you take it as a daily tablet. Oral finasteride works throughout the body and it has the largest and longest evidence base of any hair loss treatment. However, because it lowers DHT everywhere rather than only at the scalp, it is also the form responsible for most the recognised sexual and psychiatric side effects which we will discuss later.
• Topical finasteride: This is also a prescription only medicine but is it not licensed. You apply it directly to the scalp and it comes in several forms including a solution, gel, spray or compounded serum. The aim is to act at the hair follicles whilst keeping exposure to the rest of the body low. The evidence of topical finasteride is maturing. A phase III randomised controlled trial of a 0.25% topical finasteride spray, which enrolled 458 men, found it increased hair count significantly more than placebo and to a degree numerically similar to the tablet. Crucially, plasma finasteride levels were over 100 times lower than with the oral form. In other words, a similar effect at the scalp with roughly half the systemic DHT suppression.

Is Finasteride Available in the UK?

This is an important question, and the answer depends on the form. There are three different ways you can prescribe finasteride in the UK for hair loss:

• Licensed (oral 1mg): Finasteride 1mg, sold as Propecia and as generic versions, is licensed for male pattern hair loss in men aged 18 and over. This is the only finasteride product with a UK licence for hair loss. It is not available on the NHS, so it is a private prescription only.
• Off-label (oral in women): Using the oral tablet in women falls outside its men-only licence, so this counts as off-label use. It is only usually considered in postmenopausal women and with the restrictions we cover below.
• Unlicensed (topical): Topical finasteride is not licensed for hair loss in the UK but can be prescribed as an unlicensed compounded treatment if a medical prescriber deems it appropriate. It is not available off-the-shelf from standard pharmacies. Topical finasteride requires formulation by a specialist compounding pharmacy who make it for each patient based on a valid prescription.

These three terms cause a lot of confusion, so it is worth being clear about them. A licensed medicine is one a regulator has formally approved for a specific use. An off-label medicine is a licensed product used outside its approved terms. An unlicensed medicine is one made to order for each individual patient without a product licence. This is how compound treatments work. All three are legal and routine in UK medicine. We explain this in more detail in our guide to licensed, off-label and unlicensed medicines.

What Doses & Concentrations of Finasteride are Typically Available for Hair Loss?

Dosing depends on the form as well as whether its use is licensed or otherwise. For oral finasteride, the licensed dose for hair loss is 1mg once daily. This is the dose you find across the major trials and the one with the longest track record. However, there is also growing interest in microdosing oral finasteride which means taking doses below 1mg. The reason this is plausible is that finasteride’s effect on DHT is logarithmic rather than linear. In other words, most of the DHT suppression happens at very low doses, with only small gains as the dose rises. A landmark dose-ranging study showed scalp DHT was already reduced by around 62% at 0.05mg compared with 64% at the standard 1mg. Some doctors may prescribe microdose finasteride off-license on a patient by patient basis.

For topical finasteride, the most studied concentration in trials is 0.25% but there is no licensed strength and microdosing topical finasteride is becoming more common. Much lower concentrations are also increasingly in use to keep absorption to a minimum and attempt to reduce risk of side effects. How often you apply it also matters as much as the strength. Many clinics, including City Skin Clinic, compound topical finasteride across a range of concentrations typically from 0.001% up to 0.25% depending on each patients needs individual. It is also possible to combine it with minoxidil, tretinoin, melatonin or caffeine in a single formula. In practice, the concentration and frequency require a balance between optimising the effect on the scalp and reducing systemic exposure.

What Results Can You Expect from Finasteride?

Finasteride is one of the most reliable hair loss treatments available. That said, expectations are where much of the disappointment comes from, so it is important to keep the following in mind:

• Most men keep their hair: The pivotal trials followed 1,553 men for up to five years. At five years, photographic assessment rated 48% of men on finasteride as improved and a further 42% as unchanged, meaning around 90% had no further visible loss. The placebo group steadily worsened. A separate analysis found finasteride produced a 93% reduction, relative to placebo, in the likelihood of further visible loss. This of course depends on consistent use.
• 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. This is because hair grows slowly, and the drug works one step upstream of growth.
• Expect a shed first: Some men notice more shedding in the first few weeks. This is unsettling but normal and it 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 over 6 to 12 months including any hair you regrew.

Does Finasteride Work on a Receding Hairline?

This is one of the most common questions about finasteride and the honest answer has some nuance. Finasteride works best at the crown and mid-scalp. The frontal hairline and the temples are harder. The Propecia licence itself states that its effect on the temples is still in question. A long-term study bears this out, finding the vertex improved in around 90% of men but the frontal hairline in closer to 44%.

This does not mean finasteride does nothing for the hairline. By lowering DHT across the whole scalp, it still helps defend the frontal region. It is most useful for a receding hairline caught early, before those follicles have miniaturised away completely. The realistic goal at the hairline is to hold the line and thicken what is already there.

There are a couple of practical points that may also help navigate this. The first is that this is exactly why you often combine finasteride with minoxidil and microneedling. These work through different mechanisms and can help where DHT suppression alone is not enough, particularly at the front. The second is that it is worth knowing the difference between a genuinely receding hairline and a mature hairline. A maturing hairline is a normal part of getting older rather than a sign of pattern hair loss.

Is Finasteride Safe?

Finasteride is effective and for the most part safe. However, there are some serious potential risks that are, rightfully so, getting a lot of attention and regulatory scrutiny. The most serious side effects are due to systemic absorption and how much DHT suppression it causes across the whole body. If finasteride significantly lowers DHT systemically, then it can lead to a wide range of side effects including:

• Sexual: Decreased libido, erectile dysfunction and reduced ejaculate volume. These are the most common sexual side effects. In a minority of men they can persist even after stopping finasteride.
• Mood and psychological: Depression, anxiety and even suicidal thoughts.
• Breast: Tenderness, enlargement (gynaecomastia) or discharge. Get medical review of any new breast lumps or changes promptly.
• Reproductive: Testicular pain, and reduced fertility or semen quality that tends to improve after stopping.
• Prostate: A possible increased risk of high-grade prostate cancer. Finasteride also lowers PSA, which can mask the detection of prostate cancer.
• Allergic reactions: Rash, itching or swelling of the lips and face.

These side effects can occur with any form of finasteride. In theory, however, they are less likely with the topical form, because far less of the drug reaches the bloodstream. Topical finasteride also carries possible local side effects on the area where you apply it. These include scalp irritation, itching and dryness. They are usually mild and tend to settle as the skin adjusts. Side effects usually settle once treatment stops. In a small number of men, though, sexual, psychological and physical symptoms continue long after stopping, a controversial and still poorly understood condition known as post-finasteride syndrome.

UK regulators have strengthened their warnings on finasteride in recent years. Following a safety review in 2024, the MHRA introduced a patient alert card in every finasteride pack. A further review in 2025 provided confirmation that finasteride is can cause depression, suicidal ideation and sexual dysfunction that may persist after treatment stops. Anyone taking finasteride who develops depression or suicidal thoughts should stop it and contact a healthcare professional as soon as possible. Always raise any side effects (sexual or otherwise) immediately with your prescriber. This is one of the reasons finasteride is a prescription only medicine that requires medical monitoring.

What Other Treatments Work Best with Finasteride?

Finasteride tackles the hormone that drives pattern hair loss, but it does not stimulate growth directly. This is why it is so often combined with treatments that work in other ways, so their benefits add up rather than overlap. The actives most often combined with finasteride are:

• Minoxidil: The best-evidenced partner by far. It prolongs the growth phase and improves blood flow to the follicle, which is a completely separate mechanism from DHT suppression. Randomised control trials often show that topical minoxidil and finasteride together work better than either alone. The two can also be compounded into a single treatment.
• Tretinoin: This retinoid improves how well topical actives are absorbed and prolongs their activity at the follicle, which is why a compounded formula containing it is often applied once daily rather than twice.
• Microneedling: This boosts absorption of topical treatments and stimulates the follicle through the skin’s own healing response. It is particularly useful at the stubborn frontal hairline.

Because the benefits of finasteride depend on continued use, stopping means the loss will gradually return over 6 to 12 months. If you are considering it, make it an informed decision and discuss it with your clinician first. Our posts on what to do after stopping treatment and alternatives to finasteride cover best options.

Who Can and Cannot Use Finasteride?

Finasteride suits many adults with androgen-driven hair loss, but it is not right for everyone. People who whould avoid or exercise caution when it comes to using finasteride include:

• Postmenopausal women: Finasteride is sometimes used off-label for postmenopausal women, usually where minoxidil alone has not been enough. The topical form is the more cautious route because so little reaches the bloodstream. It is worth knowing that the trial of the 1mg tablet in postmenopausal women did not show benefit, so any use in women is carefully considered rather than routine.
• Premenopausal women: Women who are pregnant, breastfeeding or trying to conceive must not use finasteride in any form. They must also not handle broken tablets and avoid contact with the topical form. This is because it can interfere with the genital development of a male foetus. Few doctors will prescribe it for premenopausal women in any case.
• Anyone with a history of depression or anxiety: Should raise this with their prescriber first due to the very serious and tragic potential effects on mental health including suicide.
• Adults only: Finasteride can not be used under the age of 18.

Before starting any treatment, it is worth confirming the cause of your hair loss. Finasteride does nothing for shedding driven by iron deficiency, thyroid problems or a scarring alopecia, all of which need treating in their own right.

How to Get Finasteride in the UK

The licensed tablet is a private prescription only and is not available on the NHS. Topical finasteride, being unlicensed, is offered by clinics that provide compounded prescription treatments. Checkout our reviews of how to access prescription hair loss treatments including finasteride if appropriate in the UK.

At City Skin Clinic, we believe hair loss treatment should be personal. We provide compounded hair loss treatments containing topical finasteride 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 for women service. Book a 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. Finasteride is a prescription-only medicine and should be used only under the supervision of a qualified prescriber. Always read the patient information leaflet and report any suspected side effects to the MHRA via the Yellow Card scheme.