Finasteride for Hair Loss: What It Does, Side Effects, and Who It's For

Finasteride is the most effective hair-loss treatment for men, and also the one people are most nervous about. Both reputations are earned. Here is what it does, what the evidence shows, the side effects in plain words, and who should not take it.

I am a stylist, not a doctor, and this is not medical advice. Finasteride is a prescription drug. The decision belongs to you and a licensed prescriber.

What it does

In pattern hair loss, a hormone called DHT gradually shrinks hair follicles in genetically sensitive areas, the temples and crown in men, until they produce thin, short hairs and then none. DHT is made from testosterone by an enzyme. Finasteride blocks that enzyme, lowering DHT in the scalp and the blood substantially. Less DHT means the shrinking slows or stops, and some shrunken follicles recover.

The standard dose for hair loss is 1 mg a day, taken as a tablet. It was approved by the FDA for male pattern hair loss in 1997 and has been widely used since, so there is a long track record behind it.

What results to expect

In the original two-year trials, most men taking finasteride had no further visible hair loss, compared with roughly a quarter of men on placebo, and many had measurable regrowth. Results are best at the crown and less dramatic at the front hairline. Long-term follow-up studies suggest the benefit holds for years in most men who keep taking it.

The timeline matters. You will see nothing for the first three months. Improvement typically shows between six and twelve months, and a fair judgment needs a full year. Take photos before you start, in the same light, and compare every three months rather than every morning.

Finasteride keeps hair; it does not create a new head of it. Men who start early, when thinning is first visible, keep the most. And it works only while you take it: stop, and over the following year the hair it was protecting goes the way it was going.

Side effects, plainly

Most men who take finasteride have no side effects. A minority do, and you should know what they are before you start, not discover them.

Sexual side effects. Lower sex drive, difficulty with erections, and changes in ejaculation are the best-known. In the trials they occurred in a small percentage of men, slightly more often than in men taking placebo, and usually resolved after stopping, sometimes even while continuing. Knowing about them in advance can itself make people anxious, which is part of why they are hard to study.

Mood. The FDA-approved labeling now includes reports of depression and suicidal thoughts. If your mood changes on finasteride, stop and talk to your prescriber promptly. If you have a history of depression, discuss it before starting.

Persistent symptoms. A small number of men report sexual, mental, or physical symptoms that continue after stopping, sometimes called post-finasteride syndrome. How often this happens and what causes it are not settled, but the reports are taken seriously by regulators and should be taken seriously by you.

Breast changes. Rarely, tenderness or enlargement. Report any lump to a doctor.

PSA tests. Finasteride lowers PSA, the blood test used to screen for prostate cancer, by about half. Tell any doctor who orders a PSA test that you take it, so the number is read correctly.

Who should not take it

Finasteride is not approved for women, and women who are or may become pregnant must not take it or handle crushed or broken tablets, because it can cause abnormalities in the genitals of a male baby. Intact, coated tablets are not a handling risk, but keep them away from anyone who might be pregnant. Some doctors prescribe finasteride off-label to women after menopause; that is a specialist decision, covered on our women's hair loss page.

Men with liver disease, a history of depression, or plans to father a child soon should discuss those with the prescriber first. It is not for children.

Topical finasteride

Some online programs offer finasteride as a spray or solution applied to the scalp, often combined with minoxidil. The idea is to treat the scalp while keeping blood levels lower, which may reduce side effects. Early research is encouraging, but there is far less evidence than for the tablet, and most topical versions are compounded by a pharmacy rather than manufactured and FDA-approved. Some of the drug still reaches the bloodstream. It is a reasonable option to discuss if you are worried about side effects, not a side-effect-free version of the pill.

Combination products

Telehealth companies often sell finasteride combined with minoxidil in one tablet or one topical. Each ingredient has evidence on its own, and using both is a standard approach. But a combination product made by a compounding pharmacy has not itself been tested or FDA-approved, and you cannot adjust one ingredient without changing the other. Ask exactly what is in it, at what doses, and why.

Dutasteride

A related drug that blocks DHT more completely. It is approved in the United States for enlarged prostate, not hair loss, though it is prescribed off-label for hair and approved for it in some other countries. It may be somewhat more effective than finasteride and stays in the body much longer, which matters if side effects appear. It is usually a second step, not a first one.

Getting a prescription

Your doctor, a dermatologist, or an online telehealth program can prescribe finasteride. Generic finasteride is inexpensive at most pharmacies, often much cheaper than branded online subscriptions, so compare the monthly cost before you sign up for anything. If you want a dermatologist to prescribe a topical finasteride or a custom combination rather than the plain tablet, Happy Head is a provider I link to: dermatologist-reviewed, custom-compounded topicals and capsules, at a higher price than generic. It also sells plain oral finasteride. An online program is reasonable for straightforward male pattern hair loss. For anything patchy, sudden, or inflamed, see a dermatologist in person; that is a different problem, explained on our hair loss treatments overview.

Questions to ask before you start

• Is my hair loss pattern hair loss, or could it be something else?
• Is this the standard 1 mg tablet, a topical, or a compounded combination?
• Which side effects should make me stop and call you?
• How will we judge whether it is working, and when?
• What does it cost each month, and is generic cheaper at my pharmacy?

While you wait for results, treat your hair gently. Thinning hair is fragile hair, and breakage on top of thinning makes everything look worse than it is.

Disclosure: this page contains affiliate links. If you sign up with a provider through one of them, I may earn a commission at no extra cost to you. That does not change what I write. How this works.

Peter Louis is a Manhattan stylist and salon owner and the founder of Bombshell Brush. This article is not medical advice. Talk to a licensed prescriber before starting finasteride or any medication.