Finasteride for Hair Loss: How It Works, Results and Side Effects

Finasteride is a daily tablet that slows male pattern hair loss by lowering DHT, the hormone that shrinks genetically sensitive hair follicles. In the trials that led to its approval, men who took it for two years had clearly more hair on the crown than men on placebo, who kept thinning.^[1] The catch is simple: it only works while you keep taking it.

Below you will find how finasteride works, what the first year looks like, how often side effects really happen, and where it fits next to minoxidil, dutasteride and a hair transplant.

How Finasteride Works and What Results to Expect

How Finasteride Lowers DHT

Your body makes DHTGlossaryDihydrotestosterone (DHT) is a potent androgen that the body makes from testosterone using an enzyme called 5-alpha reductase. In people who are genetically sensitive to it, DHT makes hair follicles shrink.
Open in the glossary → from testosterone with an enzyme called 5-alpha reductase. Finasteride blocks the type 2 form of that enzyme, so less DHT is made in the blood and in the scalp.^[1]

How much less? In a study of 249 men who had scalp biopsies before and after 42 days of treatment, 1 mg a day lowered scalp DHT by 64% and blood DHT by 71%. Even 0.2 mg a day produced the maximum fall.^[2]

Testosterone does not drop. In the official prescribing information, average testosterone rose by about 15% and stayed within the normal range.^[3] For the hormone itself, and why some follicles react to it while others do not, read our entry on DHT and hair loss.

Oral or Topical Finasteride: 1 mg, 5 mg and Spray

Most of the evidence comes from the 1 mg tablet. A spray applied to the scalp was tested more recently, in a 24 week trial of 458 men at 45 centres in Europe.^[5]

In that trial the spray grew about as much hair as the tablet, while peak finasteride levels in the blood were more than 100 times lower.^[5] Its record covers 24 weeks, against five years for the tablet, so the tablet has the longer track record.^[6]

Does Finasteride Regrow Hair? Crown Versus Hairline

Yes, for many men, although holding on to the hair you have is the larger effect. In the two main trials of 1,553 men aged 18 to 41, men on finasteride had 107 more hairs than men on placebo after one year and 138 more after two, counted in a 1 inch circle of thinning crown.^[1]

The other half of the story is what happened without treatment. After 12 months, 58% of men on placebo had lost more hair, against 14% on finasteride. At five years the figures were 100% and 35%.^[3]

The front of the scalp responds too. A one year trial in men thinning at the front and middle of the scalp found a significant rise in hair count there, which held through a second year.^[8] Where the temples are already smooth skin, there is no thinning hair left for the tablet to protect.

Finasteride Results Timeline, Month by Month

Give it a full year before you judge it. Hair that has stopped thinning is a result in its own right, because men on placebo lost hair year after year.^[1]

Why Finasteride May Not Work for You

• It is not pattern hair loss. Finasteride is indicated for male pattern hair loss only.^[3] Sudden shedding all over the scalp may be telogen effluvium, and round bald patches suggest alopecia areata.
• You stopped too early. Benefit usually takes three months or more to show.^[3]
• You are a woman past menopause. In a one year trial of 137 women, 1 mg a day did no better than placebo.^[9]
• You respond less than average. Even on finasteride, 35% of men in the five year data had fewer hairs than at the start.^[3]

How to Track Your Results

The trials judged results partly from photographs reviewed by an expert panel.^[1] You can copy the idea at home:

1. Take photos before your first tablet, in the same spot and light, with dry hair and no styling products.
2. Shoot the front, the top, the crown and both temples.
3. Repeat the same shots at 6 and 12 months, then once a year.
4. Compare the sets side by side with your doctor rather than in the bathroom mirror.

Finasteride Side Effects and Safety

How Common Are Sexual Side Effects?

In the first year of the main trials, 3.8% of men on finasteride reported a sexual side effect, against 2.1% on placebo.^[3] The breakdown:

• Lower sex drive: 1.8% on finasteride, 1.3% on placebo
• Erection problems: 1.3% against 0.7%
• Ejaculation problems, mostly less semen: 1.2% against 0.7%

These effects went away in men who stopped and in most of those who carried on. By the fifth year, each one was reported by 0.3% of men or fewer.^[3]

Pooling 15 placebo-controlled trials with 4,495 men, one meta-analysis put the extra risk of sexual dysfunction on finasteride at about two thirds (relative risk 1.66).^[10] In absolute terms the numbers stay small: a 2026 review found sexual side effects in 1.9% to 6.7% of men on finasteride 1 mg, against 0.9% to 3.9% on placebo, with most mild and reversible.^[11]

Mood Changes and Post-Finasteride Syndrome

The prescribing information lists depression, suicidal thoughts and suicidal behaviour among effects reported since approval, along with sexual problems that continued after stopping.^[3] These come from voluntary reports, so their true frequency cannot be estimated reliably.

Here the evidence points two ways. The five year placebo-controlled data found no new safety concerns with long-term use.^[6] A 2021 analysis of the World Health Organization's safety database, however, found more reports of suicidal thoughts and of depression or anxiety in finasteride users than expected, mainly in men under 45 taking it for hair loss. Its authors say the signal may reflect a rise in reporting after 2012, younger men being more vulnerable, or both.^[12]

If your mood drops while you take finasteride, tell your doctor promptly. What is known about symptoms that persist after stopping is covered in our entry on post-finasteride syndrome.

Testosterone and Fertility

Testosterone goes up slightly rather than down.^[3] Sperm is a closer call. In a one year trial of 99 healthy men, finasteride 5 mg lowered total sperm count by 34% at six months, but the fall was no longer significant at one year or six months after stopping.^[13] The label also lists reports of male infertility and poor semen quality, with improvement reported after stopping.^[3] If you are trying for a baby, mention finasteride when you plan any semen test.

Finasteride for Women

Finasteride is not approved for women.^[3] In the one large trial, 137 women past menopause took 1 mg a day for a year and did no better than placebo.^[9] For treatments that do have evidence in women, read about female pattern hair loss and spironolactone.

PSA Tests in Men Over 40

Finasteride lowers PSA, the blood marker used to screen for prostate cancer. In men aged 40 to 60 taking 1 mg a day, PSA fell by a median of 40% to 50% within 48 weeks, so the reading should be doubled, as doctors already do for the 5 mg dose.^[4] Tell whoever orders your PSA test that you take finasteride. Any confirmed rise from your lowest reading needs checking, even inside the normal range.^[3]

What Happens If You Stop Taking Finasteride?

The benefit fades. Men switched from finasteride to placebo after one year lost their gain within the next 12 months.^[3]

Timing matters too. Men who started a year late gained hair once they began, but never caught up with men who started straight away, and that gap held for the rest of the five years.^[3]

Finasteride With Minoxidil, Dutasteride or a Hair Transplant

Finasteride With Minoxidil

Finasteride lowers DHT, while minoxidil acts on the follicle through a different route, so the two are often combined. In a 12 month trial of 450 men, 80.5% improved on finasteride, 59% on minoxidil 5% and 94.1% on both.^[14] A meta-analysis of five randomized trials also rated the combination above either drug alone, with no rise in side effects.^[15] Our minoxidil entry explains how to use it.

Finasteride vs Dutasteride

Dutasteride blocks both forms of 5-alpha reductase, type 1 and type 2. In a 24 week trial of 917 men, dutasteride 0.5 mg grew more hair than finasteride 1 mg, with a similar number of side effects.^[16] A network meta-analysis agreed at 24 weeks, but at 48 weeks finasteride 1 mg gave the largest gain in thick terminal hairs.^[7] The full comparison is in our dutasteride entry.

Finasteride Before and After a Hair Transplant

A transplant moves follicles from the donor areaGlossaryThe donor area is the back and sides of the head, where follicles resist DHT. An extracted follicle does not grow back in that spot, so extractions are spread out, and the donor supply is the limit of every plan.
Open in the glossary → to the thinning zone. It does nothing for the native hair around the grafts, and that hair can keep miniaturizing, eating into the result.^[17]

In a trial of 79 men, finasteride taken from four weeks before surgery until 48 weeks after improved hair density around the grafts. Visible gains at the front and top of the scalp were recorded in 94% of men on finasteride, against 67% on placebo.^[17]

Frequently Asked Questions

Is Finasteride Right for You?

Finasteride suits men with pattern hair loss who still have thinning hair to protect and who are willing to take a tablet every day for as long as they want the effect. Its placebo-controlled record runs to five years.^[6] Side effects are uncommon but real, and they deserve an open conversation with your doctor before you start.

If you are weighing finasteride against a transplant, or thinking about both, send us three photos for a free hair analysis. The medical team will tell you whether your pattern of loss suits medication, surgery or a mix of the two. You can also message us on WhatsApp.