How hair loss treatments work
Plain-English explainers for how finasteride, dutasteride and minoxidil act on pattern hair loss, and the limits of what they can do.
The basic problem we're fixing
In male and female pattern hair loss (androgenetic alopecia), the issue isn't that hair stops growing. The issue is that follicles in genetically susceptible scalp areas shrink: each growth cycle produces a slightly finer, slightly shorter hair, until eventually the follicle stops producing visible hair at all.
The hormone driving that shrinkage is dihydrotestosterone (DHT), a downstream product of testosterone. Medicines act on this in two ways: lowering DHT, and stimulating the surviving follicles to grow.
Finasteride lowers DHT by blocking the type II form of 5-alpha reductase. Dutasteride, which is used off-label for hair loss, blocks both type I and type II (see finasteride vs dutasteride and our DHT entry). Minoxidil acts on the follicle itself.
Finasteride
Stop DHT being made in the first place
Finasteride is a once-daily oral tablet that blocks the enzyme 5-alpha reductase. That enzyme is what converts testosterone into DHT. Block the enzyme, you get less DHT, and the follicle shrinkage that DHT causes slows down or reverses.
The UK product information says three to six months of once-daily treatment are generally needed before evidence of stabilisation of hair loss can be expected, and that continuous use is recommended to sustain the benefit. For many men, working means losing less hair rather than visible regrowth, and results vary between individuals.
Side effects require honest discussion at clinical review. Sexual side effects (reduced libido, erectile dysfunction, ejaculation disorders) and mood changes (low mood, anxiety, depression and rarely suicidal thoughts) have been reported. The MHRA Drug Safety Updates on finasteride (29 April 2024 and 11 May 2026) introduced patient alert cards into finasteride packs and recognise that sexual dysfunction may persist after discontinuation in a small number of cases. The 2026 update added a precautionary warning for dutasteride. Your clinician will walk you through the full picture before prescribing, and you should stop and seek advice if any of these effects occur. Finasteride is not licensed for women and must not be handled (as a crushed or broken tablet) by women who are or may become pregnant.
How it works
How it works
Minoxidil
Push the follicle to grow harder, longer
Every hair follicle cycles through three phases: a long growth phase (anagen), a short transition phase (catagen), and a resting phase (telogen) where the hair eventually sheds. In pattern hair loss, the growth phase gets shorter each cycle, so hairs are finer and don't grow as long before they fall.
Minoxidil extends the growth phase and may also improve blood flow to the follicle. The full mechanism is still being studied. Results vary between people, and the benefit lasts only while you keep using it.
Available as a topical solution applied to the scalp daily, or as a low-dose oral tablet. The oral form is prescribed off-licence in the UK for hair loss (its licensed use is for high blood pressure) so your clinician will explain the off-licence status and the options before you decide.
Using more than one medicine
Finasteride and minoxidil act by different routes: one lowers DHT, the other acts on the follicle. Some people are prescribed both, either as separate products or as a compounded topical, which is an unlicensed special. Whether to use one, both or neither is an individual prescribing decision, and this page makes no claim that one approach works better than another.
There are situations where we prescribe only one (or neither). A clinical review is the only way to know what's right for your case.
A note on side effects. Both medications have well-documented side-effect profiles. The vast majority of patients tolerate them without issue, but a small minority experience side effects that warrant adjusting or stopping treatment. Your clinician will discuss the full picture honestly at clinical review , informed consent is part of the standard of care.
Who these medications will not help
Most pages about hair loss treatment only describe who they work for. That is the easier page to write and the less useful one to read. These medicines are genuinely effective for the thing they treat, and there are several situations where they will not do what someone is hoping, and one where taking them instead of something else causes permanent harm.
They hold on to hair better than they bring it back
This is the single most common mismatch of expectations. Finasteride and minoxidil are far more reliable at slowing or stopping further loss than at regrowing what has already gone. A good number of men on treatment look broadly the same in two years as they do today, and that is the treatment working, not failing. Where regrowth does happen it is most likely at the crown and mid-scalp, and least likely at a receded frontal hairline.
They cannot replace a follicle that is no longer there
These drugs rescue follicles that are miniaturising: still present, producing finer and shorter hairs each cycle. They cannot create new ones. Where an area has been completely smooth for years, there is usually nothing left to rescue, and no dose or combination changes that. On the Norwood scale, treatment tends to have most to work with in the earlier stages, and progressively less as loss becomes advanced and long-established. If the goal is coverage of an area that is already bare, that is a surgical question rather than a medical one.
They do not treat scarring alopecias, and using them alone can cost you hair
Conditions such as frontal fibrosing alopecia, lichen planopilaris and central centrifugal cicatricial alopecia destroy the follicle through inflammation and replace it with scar tissue. That damage is permanent. Finasteride and minoxidil do nothing about the inflammation driving it, so taking them alone can mean months pass while follicles are still being lost. Signs worth taking seriously are a hairline moving back in a band with loss of the eyebrows, redness or scaling around the follicles, itching or burning, or smooth shiny patches with no visible pores. If any of that fits, the priority is assessment, sometimes with a biopsy, not a prescription.
They are the wrong answer for sudden diffuse shedding
Hair coming out all over the scalp over a few weeks, rather than thinning in a pattern, is more often telogen effluvium: a reaction to illness, surgery, childbirth, rapid weight loss, low iron or a thyroid problem. It usually recovers once the cause is dealt with, and treating it with finasteride addresses nothing. Bloodwork is the useful first step here.
They do not treat alopecia areata
Well-defined round or oval bald patches appearing quickly are usually alopecia areata, an autoimmune condition with an entirely separate treatment pathway. It is not androgenetic hair loss and does not respond to DHT blockade.
Two other things worth knowing before starting. Judge it at twelve months, not three. Shedding in the first two months is common and is not the treatment failing. And the effect depends on continuing. Stop, and hair held on to by treatment is generally lost over the following six to twelve months, arriving at roughly where you would have been without it. That is worth deciding on deliberately at the start rather than discovering later.
If any of the above sounds like your situation, our prescriber will say so rather than issue a prescription that will not help. Depending on what is going on that may mean bloodwork to find a treatable cause, a scarring alopecia workup, or a surgical opinion. Being told a medication is not right for you is a better outcome than a year spent finding out.