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Finasteride has the strongest evidence of anything we have for male pattern hair loss, and I still spend most of the visit on side effects. Trials put sexual side effects at a few percent, barely above placebo, and most men settle — but some report problems that did not resolve after stopping, and I will not pretend that question is closed. It holds hair better than it regrows it, so start early, give it a year, and take photographs. If you are on the fence, start and watch — almost everyone who stops for a side effect is back to normal within weeks.
— Dr. Schwarz, Board Certified Dermatologist
Key Facts
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| Also called | Propecia, Proscar (the 5 mg prostate tablet), generic finasteride |
| Drug class | Type II 5-alpha reductase inhibitor |
| Taken as | Tablet, once a day |
| Typical course | Long term, for as long as you want the effect |
| Time to work | 3 to 6 months, judged at 12 months |
| Prescription only | Yes |
What It Is
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Finasteride is a prescription tablet that lowers DHT, a hormone made from testosterone. It was approved in the United States in the 1990s at 1 mg a day for male pattern hair loss in men, and at 5 mg a day for an enlarged prostate. It is not approved for women and is not used in anyone who is pregnant or could become pregnant. Some doctors prescribe it off-label for female pattern hair loss after menopause, on much thinner evidence.
How It Works
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Pattern hair loss is not hair falling out; it is hair shrinking. In people who carry the genes for it, scalp follicles react to DHT by making a finer, shorter, paler hair each cycle until what grows is barely visible — miniaturization. DHT comes from testosterone via an enzyme called 5-alpha reductase, and the scalp version is mostly type II. Finasteride blocks type II, so less DHT is made. At 1 mg a day it lowers DHT by roughly two thirds in the blood and in the scalp.
Removing the signal stops follicles shrinking and lets some shrunken ones grow back thicker. That explains the rest of the drug: it holds well, regrows modestly, does most where hair is thin rather than bare, and does nothing for a follicle that is gone. Testosterone is not lowered — it rises slightly, because less is converted.
Here is where Finasteride acts in the skin, and what the others do instead.
About Finasteride
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Skin basics
Pattern hair loss is the follicle shrinking a little more each cycle in response to a hormone signal. Finasteride blocks that signal, which slows or stops the shrinking. It protects what is there more than it regrows. Blocks one of the two enzymes making DHT.
Finasteride arrives from the inside, carried to the skin by the blood, rather than crossing the barrier from outside. That is why it works everywhere at once, and why it needs monitoring.
This works on the follicle itself, lengthening the growing phase and widening a shrunken follicle. Hairs already lost can come back, but only while treatment continues — stopping returns things to where they were.
The outer film of dead cells and oil. It holds water in and keeps irritants out, and it is thinner than a sheet of paper. Almost every dry, itchy, stinging skin problem starts here.
The outer layer, and the only one anything in a jar reaches. It renews itself constantly: a cell made at the bottom takes about a month to reach the surface and flake off. Most of what a skincare product does, it does here.
The living layer underneath, holding the blood vessels, the nerves and the collagen. It is where lasting change happens and it is hard to reach: most of what is sold for the skin never gets this far.
What It Treats
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Not the Best For
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Forms
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Finasteride for hair loss is a small film-coated 1 mg tablet taken once a day. The coating keeps the drug off the fingers of whoever handles it.
The 5 mg prostate tablet is the same drug at five times the dose. Splitting it to save money breaks the coating and exposes the powdered core — a poor choice in any household where someone is or could become pregnant.
Compounded topical finasteride, alone or mixed into minoxidil spray, is also sold. Less reaches the bloodstream, which is the appeal, but some still does, strengths vary between pharmacies, and the evidence is much smaller.
Strengths
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There is only one hair loss dose. The strengths below are about which tablet you are handed.
Dose
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The dose does not change with weight, and there is no build-up period. What varies is how often people take it.
How to Take It
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When to take it: Any time of day, with or without food. Attach it to something you already do — two weeks of forgetting is what ruins this drug, not a bad day. Do not split or crush the 1 mg tablet.
If you miss a dose: Take it when you remember, or skip it. Never take two at once. One missed tablet makes no difference. A missed month does.
What to Expect
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Side Effects
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Most men notice nothing. The sexual effects are the ones people ask about, and they affect a small minority.
Common — expected, and they settle
- Lower sex drive
- Trouble getting an erection
- Less semen The volume, not the sperm count.
- Breast tenderness
Tell your doctor — worth a call, not an emergency
- Sexual effects that do not settle after stopping
- Low mood or loss of interest in things Raise it rather than sitting with it.
- A breast lump, pain or nipple discharge Needs looking at.
- A PSA test coming up Finasteride roughly halves the result. Tell whoever reads it.
Stop and get care
- Hives, facial swelling or trouble breathing: A true allergic reaction is rare.
What to Avoid
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- Broken tablets near a pregnancy The coating prevents skin contact. Finasteride can affect how a male baby's genitals develop, so anyone pregnant or who could become pregnant should not handle a broken tablet. Intact tablets are fine to touch.
- Splitting 5 mg tablets in a shared house The same problem, self-inflicted. If cost is the reason, ask for generic 1 mg instead.
- Donating blood too soon after stopping Wait about a month, so a recipient who is pregnant is not exposed.
- Judging it in the first three months Nothing to see yet, and an early shed reads as failure when it is not.
- Stopping for a week to see what happens A week off tells you nothing, and stop-start use gives you the side effect risk with less of the benefit.
Monitoring
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No routine blood tests are needed for a healthy man taking 1 mg for hair loss. The honest monitoring is photographs — same spot, same light, every few months, because slow change is invisible day to day.
One number does change. Finasteride roughly halves PSA, the prostate blood test. It does not hide a problem, but the result has to be read knowing you are on it, so tell any doctor who orders one. Nothing needs checking on a schedule; the recurring question is whether you still want to take it.
If You Stop
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There is no taper and no withdrawal. DHT returns to its previous level within days to weeks. Hair follows more slowly. What you kept because of the drug is lost over about six to twelve months, leaving you roughly where you would have been anyway. Nothing ends up worse than baseline.
Cost
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Generic finasteride 1 mg is inexpensive and widely stocked — one of the cheaper long-term prescriptions in dermatology. Branded Propecia costs considerably more for the same drug. Telehealth subscriptions bundle the tablet with shipping and a consultation — convenient, and usually more per month than a local generic. Insurance often does not cover it, because hair loss counts as cosmetic, so most people pay cash.
Ask Your Doctor
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How It Compares
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Myths
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- "It causes permanent impotence." This part is genuinely unsettled and deserves a straight answer. In the year-long licensing trials, sexual side effects — lower libido, erection trouble, less semen — were reported by under 4 in 100 men on finasteride and about 2 in 100 on placebo, and in nearly everyone they resolved on stopping or while continuing. Against that, a number of men report symptoms that persisted long after stopping, sometimes with low mood. Controlled studies have not confirmed the drug causes this, and have not ruled it out. Some regulators have added wording about persistent sexual side effects and mood changes to the label.
- "It lowers testosterone and shrinks your muscles." It does the opposite — testosterone rises slightly, because less is converted to DHT. It is not a steroid and it does not reduce muscle mass.
- "It only works on the crown." Most measured regrowth is at the crown and mid-scalp, but the slowing of loss applies across the affected scalp, hairline included. Regrowing a receded hairline is what it rarely does.
- "It causes prostate cancer." A large prevention trial found fewer prostate cancers overall on finasteride, with slightly more tumors that looked high grade. Later analysis suggested that was mostly because a smaller prostate makes an aggressive tumor easier to find, and long-term follow-up did not show more deaths. Discuss it with a doctor rather than assuming harm.
Questions Patients Ask
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How long before I know if it is working?
Six months for the first honest look, twelve for the verdict. Photographs make that possible.
Do I have to take it forever?
As long as you want the effect. Stopping puts you back on your old path within six to twelve months.
Are the sexual side effects permanent?
For almost everyone they do not happen or they resolve. A minority report symptoms that persisted after stopping, and research has neither confirmed nor ruled that out. Worth discussing before you start.
Can my partner touch the tablets?
Whole, coated tablets are fine. Broken or crushed ones should not be touched by anyone pregnant or who could become pregnant.
Is my hair falling out more since I started?
It can, in the first weeks, as weak short hairs are replaced. It usually settles by month three. Still climbing at four months, get it looked at.
Can I take it with minoxidil?
Yes, a common pairing. They work on different parts of the problem, so the effects add up.
References
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- Adil A, Godwin M. The effectiveness of treatments for androgenetic alopecia: A systematic review and meta-analysis. Journal of the American Academy of Dermatology. 2017. — Journal of the American Academy of Dermatology, 2017
- Gupta AK, Mays RR, Dotzert MS, et al. Efficacy of non-surgical treatments for androgenetic alopecia: a systematic review and network meta-analysis. Journal of the European Academy of Dermatology and Venereology : JEADV. 2018. — Journal of the European Academy of Dermatology and Venereology : JEADV, 2018
- Lee S, Lee YB, Choe SJ, et al. Adverse Sexual Effects of Treatment with Finasteride or Dutasteride for Male Androgenetic Alopecia: A Systematic Review and Meta-analysis. Acta dermato-venereologica. 2019. — Acta dermato-venereologica, 2019
- Pompili M, Magistri C, Maddalena S, et al. Risk of Depression Associated With Finasteride Treatment. Journal of clinical psychopharmacology. 2021. — Journal of clinical psychopharmacology, 2021
- van Zuuren EJ, Fedorowicz Z, Schoones J. Interventions for female pattern hair loss. The Cochrane database of systematic reviews. 2016. — The Cochrane database of systematic reviews, 2016
- Rosenthal A, Conde G, Greco JF, et al. Management of androgenic alopecia: a systematic review of the literature. Journal of cosmetic and laser therapy : official publication of the European Society for Laser Dermatology. 2024. — Journal of cosmetic and laser therapy : official publication of the European Society for Laser Dermatology, 2024