Hair loss treatment is a crowded market, and not every product on the shelf has been through the kind of trial that shows it actually works. Marketing claims and genuine clinical evidence are not the same thing: a confident label is easy to print, while a properly conducted randomised trial takes years and real scrutiny. This article sets out what the evidence genuinely supports, starting with the two medicines that have the strongest research base, then looking honestly at what falls short of that standard.
It also matters what type of hair loss you actually have. The evidence behind finasteride and minoxidil applies specifically to androgenetic (pattern) hair loss, the gradual, genetically driven thinning that follows a typical pattern at the hairline, crown or overall scalp. Sudden or patchy shedding can have other causes, such as an underactive thyroid, low iron or a recent illness, and those respond to treating the underlying cause rather than to a pattern-hair-loss medicine. A clinician can help confirm which type you are dealing with before recommending treatment.
Finasteride: what the evidence shows
Finasteride is an oral tablet, licensed in the UK for male-pattern hair loss, that blocks the enzyme responsible for converting testosterone into dihydrotestosterone (DHT). DHT is the hormone that gradually shrinks genetically susceptible hair follicles, so reducing it slows the underlying process rather than just treating the symptom. Randomised controlled trials in men with androgenetic alopecia consistently show that finasteride slows further loss in the large majority of users and produces visible regrowth in a substantial proportion, with the response building over the first year of continuous use.
This evidence base only applies to men. Finasteride is not licensed or generally recommended for female-pattern hair loss, and it must never be taken or handled by women who are or may become pregnant, because lowering DHT can affect the development of a male foetus. For a deeper look at the mechanism and side-effect profile, see our guide to how finasteride and minoxidil work.
Minoxidil: what the evidence shows
Minoxidil, usually applied as a topical solution or foam, works through a different mechanism: it is thought to extend the active growth phase of the hair cycle and improve blood flow to follicles, rather than acting on hormones at all. Its trial evidence stretches back decades and, unlike finasteride, it is supported for use in both men and women, which makes it the main evidence-backed option for female-pattern hair loss described in our guide to hair loss in women.
The catch is that the response is more variable than with finasteride: some users see clear regrowth, others mainly a slowing of loss, and a minority see little change. A temporary increase in shedding in the first few weeks is common and expected as follicles reset into a new growth phase, not a sign that treatment has failed. A low-dose oral form of minoxidil is also used off-label under clinical supervision for patients who find the topical version impractical.
Combining finasteride and minoxidil
Because finasteride targets the hormonal driver of hair loss and minoxidil acts on the growth cycle itself, the two treat the problem from different angles. Evidence from combination studies suggests that using both together tends to produce a stronger result than either used alone, which is why many prescribers consider a combined approach when a single treatment gives a partial or slow response.
| Treatment | Form | Who it's evidenced for | Evidence strength |
|---|---|---|---|
| Finasteride | Oral tablet | Men only | Strong (multiple RCTs) |
| Minoxidil | Topical or low-dose oral | Men and women | Strong (decades of trials) |
| Combined finasteride + minoxidil | Oral + topical | Men, for a partial response to either alone | Moderate-strong (fewer, smaller trials) |
| Biotin/vitamin supplements | Oral | Only those with a confirmed deficiency | Weak without deficiency |
| Hair growth shampoos/serums | Topical | Not established | Weak or absent |
Combination treatment is not automatically the right next step for everyone, though; it means taking on two routines and two sets of monitoring, so whether it makes sense depends on how you have responded so far and your clinician's assessment.
What lacks good evidence: shampoos, supplements and devices
Walk down any pharmacy aisle and you will find shampoos, serums, biotin capsules and gadgets all promising fuller hair. The honest picture is that most of these have little independent trial evidence to support hair regrowth claims. Biotin and other vitamin supplements can help hair that is thinning because of a genuine deficiency, such as low iron, low vitamin D or low B12, but topping up nutrients you are not actually short of has not been shown to regrow hair caused by androgenetic alopecia. Our guide to which vitamins genuinely help hair loss covers when testing and supplementation is worthwhile and when it isn't.
Caffeine and saw palmetto shampoos, "hair growth" serums and most over-the-counter devices generally rely on small, unreplicated or manufacturer-funded studies rather than the kind of independent randomised trials behind finasteride and minoxidil. Low-level laser therapy devices are a partial exception, with some supportive trial data, though the evidence base is still far thinner than for the two established medicines. None of this means every non-medicine option is worthless, only that the proof simply is not there in the way it is for finasteride and minoxidil, so it is worth being sceptical of confident marketing claims.
A useful habit when weighing up any product is to ask what actually backs the claim. Customer reviews and glossy packaging are not evidence; a peer-reviewed randomised trial, published in a proper journal and ideally independent of the manufacturer, is. UK regulatory status is another useful marker: finasteride and minoxidil are licensed medicines that had to demonstrate their effect to the regulator, while most hair growth shampoos and supplements are sold as cosmetics or food supplements, which face a much lower bar for the claims they can make.
Realistic timelines, whichever treatment you choose
Whatever evidence-backed option you use, patience matters more than most people expect. Hair follicles cycle slowly between growing, resting and shedding phases, so no treatment shows its effect within days or even a few weeks. Plan on at least three to six months of consistent, correct use before judging any change, and closer to a year to see the fuller picture. Stopping and restarting, or judging too early, is one of the most common reasons people wrongly conclude a genuinely effective treatment "didn't work" for them.
It also helps to set expectations correctly from the start: the realistic goal with finasteride or minoxidil is usually to slow or halt further loss and regain some density, not to restore a full head of hair from years earlier. Because both work only while continued, any gains are typically lost within months of stopping. Dated photographs taken every few months, under similar lighting, are a far more reliable way to track progress than daily mirror-checking, which rarely reveals gradual change. If there has been no response at all by around six months of consistent use, that is the point to revisit the diagnosis and the plan with a clinician, rather than persisting indefinitely with something that isn't helping.
The overall picture from the evidence is fairly simple, even if the marketing around hair loss is not: finasteride and minoxidil, used consistently and for long enough, are the two options with genuine trial support, and a clinician can help you work out whether either, or both together, fits your situation, your goals and your health history.