Finasteride
Finasteride is a tablet that blocks the enzyme converting testosterone into dihydrotestosterone, usually shortened to DHT. DHT is the hormone that shrinks susceptible follicles on the scalp over years until they stop producing visible hair, so blocking it addresses the mechanism of male pattern loss rather than its appearance.
The standard dose for hair loss is 1mg a day, which is a fifth of the dose used for prostate enlargement. It reduces scalp DHT substantially, and in most men it slows or halts loss, with a minority seeing meaningful regrowth in areas that were thinning rather than bald.
It is the only thing on this site that changes where you are heading rather than how you look on the way.
On this page
What it actually does
Hold rather than restore. Across the large trials, the large majority of men taking finasteride either kept what they had or improved over a couple of years, while the comparison groups continued to lose, and the biggest gap between the two grows with time.
Regrowth happens, mostly in the crown and mid-scalp, and mostly in follicles that were miniaturising rather than gone. A hairline that has been bare for a decade does not come back. Anyone promising that is selling something.
The result is easy to undervalue, because not losing hair looks like nothing happening. Photographs are the only way to see it, which is why the baseline set matters so much.
Before your first tablet
Take four photographs in flat daylight, front, both sides and the top of your head, and put them somewhere you will find them. In a year you will not remember what you looked like, and without the comparison you will not know whether to continue.
The side effect conversation
This deserves a straight answer rather than reassurance in either direction.
In the manufacturer trials, sexual side effects, meaning reduced libido, erectile difficulty or reduced ejaculate volume, were reported by a low single-digit percentage of men, and a meaningful number of men on placebo reported the same things. For most who experience them, they resolve on stopping and often while continuing.
There is a contested question about symptoms persisting after stopping, sometimes called post-finasteride syndrome. The literature is genuinely unsettled. It is reported, it appears to be rare, and the mechanism is not established. Both the people who dismiss it entirely and the people who describe it as common are going beyond the evidence.
Other recognised effects include breast tenderness or enlargement, which is uncommon, and an association with mood changes that is real enough to take seriously if you have a history of depression. Finasteride also lowers PSA readings, which matters for prostate screening later, so your doctor needs to know you are taking it.
The honest summary is that most men take it without trouble, a small number do not tolerate it, and it is your decision to make on the numbers rather than on a forum.
Topical finasteride and dutasteride
Topical finasteride applied to the scalp is increasingly offered, on the logic that it reduces scalp DHT with less systemic absorption. The evidence is reasonable and growing, absorption is lower but not zero, and it is a sensible option for someone who wants the mechanism with less systemic exposure.
Dutasteride blocks more of the conversion and is more potent. It is licensed for hair loss in a few countries and used off-label in many others, it has a longer half-life, and its side effect profile is broadly similar but the exposure lasts longer once you stop. It is usually a second-line option after finasteride rather than a starting point.
Both need a prescriber who will discuss them with you, not a website that will simply post them.
At your appointment
Ask what the plan is if you do not tolerate it, before you start. Knowing in advance that there is a lower dose, a topical version and an alternative makes it much easier to report a side effect honestly rather than quietly stopping.
Who should not take it
Anyone who is pregnant or may become pregnant should not take it or handle broken tablets, because it can affect the development of a male foetus. This is the one absolute rule.
Women with androgenetic loss are sometimes prescribed it off-label after the menopause or with reliable contraception, and that is a specialist conversation rather than a general one.
Trans women on oestrogen with an androgen blocker are usually already suppressing DHT substantially, and adding finasteride on top may add little. Ask the prescriber who manages your hormones rather than deciding independently.
Anyone due for prostate screening should tell the doctor doing it. Anyone with a history of significant depression should weigh the mood question with their own clinician.
Timeline and stopping
Expect a shed in the first two to three months as resting hairs are pushed out by new growth. It is normal, it is temporary, and it is where most people give up.
Give it twelve months before judging anything, with photographs. Continued benefit accrues over years.
Stopping loses everything it held, over roughly six to twelve months, and you end up approximately where you would have been. That is the deal, and there is no version of this that is a course of treatment rather than a permanent one.
Around month three
Expect the shedding phase and decide now that you will not stop during it. It is new growth pushing old hairs out, it passes, and quitting at month three is the single most common way people waste a year.
Frequently asked questions
How likely are side effects?
Low single-digit percentages in the trials, with a notable placebo rate alongside. Most men take it without trouble. See the side effect conversation.
Will it regrow my hairline?
Rarely. It holds hair and can thicken miniaturising follicles, mostly at the crown. A long-bare hairline does not come back. See what it actually does.
Do I need it if I have a transplant?
Something has to hold the untransplanted hair or the result gets stranded as loss continues. This is the usual answer.
What happens if I stop?
You lose what it held over six to twelve months. See timeline and stopping.
Is topical finasteride as good?
The evidence is reasonable and it lowers systemic exposure without eliminating it. It is a fair option for someone worried about side effects. See topical finasteride and dutasteride.