What does the research show about finasteride?

Finasteride

In men with pattern hair loss, finasteride 1 mg raised hair counts and self-rated improvement against placebo over 1 to 2 years. Erectile dysfunction about doubled in pooled trials, though absolute rates were low. Case series and adverse event databases describe sexual symptoms that persisted after stopping, and depression and suicidal thoughts. The label lists both.

Add to Bio HackChecked 2026-11-13

Status: Prescription drug in the US. FDA-approved as Propecia (1 mg) for male pattern hair loss in men and as Proscar (5 mg) for benign prostatic hyperplasia. Not approved for use in women. No topical form is FDA-approved.
Also called: Propecia, Proscar, finasteride 1 mg, 5-alpha reductase inhibitor, 5-ARI, fin
Taken for: hair loss, male pattern baldness, hairline, prostate

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

StrongShown to raise vertex hair count in men by about 107 hairs at 1 year and 138 at 2 years over placebo, from a baseline of 876.
ModerateShown to improve photographic hair scores more with topical minoxidil added than either drug alone in androgenetic alopecia. Hair density change did not differ.
ModerateShown to raise hair density and hair count in men, as a mix with minoxidil and as a spray at 24 weeks. No topical finasteride is FDA-approved.
LimitedOne trial found prostate cancer in 18.4% on 5 mg against 24.4% on placebo over 7 years in men aged 55 or older.

Reported risks6

ModerateMixed results: one review found erectile dysfunction rose, one extra case per 82 men treated, while another found no rise in overall sexual dysfunction.Common
LimitedOne trial found high-grade prostate tumors in 6.4% on 5 mg against 5.1% on placebo. The label warns of this risk and of lowered PSA.Common
LimitedCase reports: men describe low libido and erectile dysfunction lasting months to years after stopping. The label lists persistent sexual dysfunction among postmarketing reports.How often is not known
LimitedLinked to more suicidality reports in a global adverse event database, most in men under 45 and men using it for hair loss. The label lists depression.How often is not known
LimitedFDA states it received 32 reports linked to compounded topical finasteride, including sexual and mood effects, most continuing after the product was stopped.How often is not known
LimitedThe label warns that women who are or may become pregnant must not use finasteride or handle broken tablets, because of risk to a male fetus.How often is not known

What people take it for, and what was found

Shown to help4

StrongStudied in men

Scalp hair count and appearance

Shown to raise vertex hair count in men by about 107 hairs at 1 year and 138 at 2 years over placebo, from a baseline of 876.

The numbers and sources

Effect: On finasteride 1 mg, hair count in a 5.1 cm² area of the vertex rose by 107 hairs at 1 year and 138 hairs at 2 years against placebo, from a baseline of 876. The placebo group lost hair progressively [1]. Pooled, men on finasteride were more likely to report improved scalp hair in the short term (RR 1.81, 95% CI 1.42 to 2.32) and long term (RR 1.71, 95% CI 1.15 to 2.53). Mean hair count rose 9.42% more than placebo by 12 months and 24.3% more by 24 months or later. The number needed to treat for one man to rate himself improved was 5.6 short term and 3.4 long term [2].
Population: 1,553 men aged 18 to 41 over 1 year, and 1,215 in a second-year extension [1]; 12 RCTs with 3,927 men [2].
Sources: [1], [2]
Caveats: [2] rated the evidence moderate quality. Short-term self-assessment results were heterogeneous (I² 64%). The trials studied men, not women.

Moderate

Adding topical minoxidil

Shown to improve photographic hair scores more with topical minoxidil added than either drug alone in androgenetic alopecia. Hair density change did not differ.

The numbers and sources

Effect: Across 5 RCTs, finasteride plus topical minoxidil produced higher global photographic scores, more patients with marked improvement and fewer with no change or worsening than either drug alone. Hair density change and adverse events did not differ between the combination and either drug alone [3].
Population: 5 RCTs in people with androgenetic alopecia, 2 of them comparing the combination with finasteride alone [3].
Sources: [3]
Caveats: One meta-analysis of few trials. The abstract gives P values without effect sizes, and concentrations varied [3].

ModerateStudied in men

Topical finasteride

Shown to raise hair density and hair count in men, as a mix with minoxidil and as a spray at 24 weeks. No topical finasteride is FDA-approved.

The numbers and sources

Effect: Across 7 RCTs, a topical solution of minoxidil mixed with finasteride raised hair density (mean difference 9.22, P 0.04), hair diameter (mean difference 2.26, P 0.005) and global photographic scores (mean difference 0.79) more than minoxidil solution alone. Marked improvement was more likely on the mix (OR 3.29) [4]. In a 24-week phase 3 trial, topical finasteride spray raised target-area hair count more than placebo at week 24 (P under 0.05) but not at week 12 (P 0.0688). Terminal hair count and investigator-rated vertex growth also favored the spray [5].
Population: 7 RCTs with 396 men [4]; 270 Chinese men, 251 completing, randomized 2 to 1 to spray or placebo [5].
Sources: [4], [5]
Caveats: The authors of [4] rate the main results moderate certainty and note heterogeneity and small samples. The abstract of [5] gives P values without effect sizes. No topical finasteride is FDA-approved, and the products sold in the US are compounded (see Risks) [6].

LimitedStudied in men

Prostate cancer prevention

One trial found prostate cancer in 18.4% on 5 mg against 24.4% on placebo over 7 years in men aged 55 or older.

The numbers and sources

Effect: Over 7 years on finasteride 5 mg, prostate cancer was found in 18.4% against 24.4% on placebo, a 24.8% relative reduction in prevalence (95% CI 18.6 to 30.6). Urinary symptoms were less common and sexual side effects more common on finasteride [7].
Population: 18,882 men aged 55 or older with PSA of 3.0 ng/mL or lower [7].
Sources: [7]
Caveats: One trial, at 5 times the hair loss dose, in older men. High-grade tumors were more common on finasteride (see Risks) [7]. Funded by the National Cancer Institute [7].
Why limited: This rests on one trial, of 18,882 people. Strength counts independent studies that agree, so one trial is limited at any size.

Doses studied

The hair loss trials used 1 mg by mouth once daily [1][2][8]. The prostate cancer prevention trial used 5 mg once daily for 7 years [7].

Risks

Reported risks5

LimitedStudied in menCommon

High-grade prostate cancer and PSA

One trial found high-grade prostate tumors in 6.4% on 5 mg against 5.1% on placebo. The label warns of this risk and of lowered PSA.

The numbers and sources

How common: Common: between 1 in 100 and 1 in 10 people.
Effect: High-grade tumors (Gleason 7 to 10) were found in 6.4% of men on finasteride 5 mg against 5.1% on placebo over 7 years [7]. The Propecia label carries a warning on an increased risk of high-grade prostate cancer with 5-alpha reductase inhibitors and on the drug lowering PSA [10].
Population: 18,882 men aged 55 or older [7].
Sources: [7], [10]
Caveats: One trial, at 5 times the hair loss dose, in older men.
Why limited: This rests on one trial, of 18,882 people. Strength counts independent studies that agree, so one trial is limited at any size.

LimitedStudied in menHow often is not known

Sexual symptoms that persist after stopping (post-finasteride syndrome)

Case reports: men describe low libido and erectile dysfunction lasting months to years after stopping. The label lists persistent sexual dysfunction among postmarketing reports.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In interviews with men reporting sexual symptoms that lasted at least 3 months after stopping, 94% reported low libido, 92% erectile dysfunction, 92% reduced arousal and 69% orgasm problems. Mean use had been 28 months, and symptoms had lasted a mean 40 months since stopping [12]. In the FDA adverse event database, 577 reports of persistent sexual dysfunction were found among 4,910 reports in men aged 18 to 45 on low-dose finasteride, a reporting rate 28 times that of all other drugs (EBGM 28.0, 95% CI 26.1 to 30.0) [13]. The current Propecia label lists sexual dysfunction that continued after stopping, including erectile, libido, ejaculation and orgasm disorders, among postmarketing reports [10].
Population: 71 men aged 21 to 46 recruited for persistent symptoms [12]; FAERS reports from 1998 to 2013 [13]; postmarketing reports [10].
Sources: [12], [13], [10]
Caveats: [12] recruited men who already had symptoms and relied on recall, so it cannot give a rate. Database reporting ratios measure reporting, not incidence. No controlled trial measured persistence after stopping.

LimitedHow often is not known

Depression and suicidal thoughts

Linked to more suicidality reports in a global adverse event database, most in men under 45 and men using it for hair loss. The label lists depression.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In the WHO global adverse event database, finasteride had a reporting odds ratio of 1.63 (95% CI 1.47 to 1.81) for suicidality and 4.33 for psychological adverse events. The signal for suicidality was larger in men under 45 (ROR 3.47) and in men using it for hair loss (ROR 2.06), and was not found in older men treated for prostate enlargement. Reports rose after 2012 [14]. The current label lists depression and suicidal ideation and behavior among postmarketing reports [10].
Population: 356 suicidality and 2,926 psychological reports in VigiBase [14].
Sources: [14], [10]
Caveats: The authors of [14] state the signals may reflect stimulated reporting and/or greater vulnerability in younger men. Reporting ratios measure reporting, not incidence.

LimitedHow often is not known

Compounded topical finasteride

FDA states it received 32 reports linked to compounded topical finasteride, including sexual and mood effects, most continuing after the product was stopped.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: FDA reported 32 cases in its adverse event reporting system from 2019 to 2024 linked to compounded topical finasteride. Reported events included erectile dysfunction, decreased libido, anxiety, depression, suicidal ideation, brain fog, fatigue, insomnia and testicular pain, plus local irritation, redness, dryness and burning. FDA states most reports describe events that continued after the product was stopped [6].
Population: FDA Adverse Event Reporting System cases, 2019 to 2024 [6].
Sources: [6]
Caveats: Case reports cannot give a rate. The alert concerns compounded products, not the formulations tested in trials.

LimitedHow often is not known

Exposure in pregnancy

The label warns that women who are or may become pregnant must not use finasteride or handle broken tablets, because of risk to a male fetus.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The label states women who are or may become pregnant must not use finasteride or handle crushed or broken tablets, because of risk to a male fetus [10].
Population: Label statement [10].
Sources: [10]
Caveats: Label statement, not a trial rate.

Mixed results1

ModerateStudied in menCommon

Sexual side effects during treatment

Mixed results: one review found erectile dysfunction rose, one extra case per 82 men treated, while another found no rise in overall sexual dysfunction.

The numbers and sources

How common: Common: between 1 in 100 and 1 in 10 people.
Effect: Pooled, erectile dysfunction rose on finasteride (RR 2.22, 95% CI 1.03 to 4.78), one extra case for every 82 men treated. Any sexual disturbance had an RR of 1.39 (95% CI 0.99 to 1.95). Stopping for sexual side effects did not differ from placebo [2]. A second meta-analysis found an RR for sexual dysfunction of 1.66 (95% CI 1.20 to 2.30) on finasteride 1 mg [8]. A network meta-analysis found finasteride 1 mg and 5 mg did not differ from placebo in global sexual dysfunction [9]. In the label's year-one data, decreased libido occurred in 1.8% against 1.3% on placebo, erectile dysfunction in 1.3% against 0.7% and ejaculation disorder in 1.2% against 0.7% [10].
Population: 12 RCTs with 3,927 men [2]; 15 RCTs with 4,495 men on finasteride or dutasteride [8]; RCTs of finasteride and dutasteride [9]; 945 on finasteride and 934 on placebo [10].
Sources: [2], [8], [9], [10]
Caveats: The meta-analyses disagree on whether sexual dysfunction overall rises [8][9]. A review of 34 finasteride hair loss trials found none had adequate safety reporting. Funnel plots suggested sexual effects were systematically underdetected, 56% of trials were funded by the manufacturer, and 76% evaluated safety for 1 year or less [11].

Claims tested and not found

That finasteride 1 mg grows hair in postmenopausal women. After a year, hair count change did not differ between finasteride 1 mg and placebo, and photographic, investigator and biopsy assessments showed no improvement [15].

Sources

Kaufman KD, Olsen EA, Whiting D, et al. Finasteride in the treatment of men with androgenetic alopecia. Journal of the American Academy of Dermatology. 1998. https://doi.org/10.1016/S0190-9622(98)70007-6
Mella JM, Perret MC, Manzotti M, et al. Efficacy and Safety of Finasteride Therapy for Androgenetic Alopecia. Archives of Dermatology. 2010. https://doi.org/10.1001/archdermatol.2010.256
Chen L, Zhang J, Wang L, et al. The Efficacy and Safety of Finasteride Combined with Topical Minoxidil for Androgenetic Alopecia: A Systematic Review and Meta-analysis. Aesthetic Plastic Surgery. 2020. https://doi.org/10.1007/s00266-020-01621-5
Li Y, Huang Q, Zhou Z, Zhang Y. Comparing minoxidil-finasteride mixed solution with minoxidil solution alone for male androgenetic alopecia: a systematic review and meta-analysis of randomized controlled trials. Frontiers in Medicine. 2025. https://doi.org/10.3389/fmed.2025.1632139
Zhou C, Yang B, Zeng H, et al. Efficacy and safety of topical finasteride spray solution in the treatment of Chinese men with androgenetic alopecia: A phase III, multicenter, randomized, double-blind, placebo-controlled study. Chinese Medical Journal. 2026. https://doi.org/10.1097/cm9.0000000000003495
U.S. Food and Drug Administration. FDA alerts health care providers, compounders and consumers of potential risks associated with compounded topical finasteride products. 2025. https://www.fda.gov/drugs/human-drug-compounding/fda-alerts-health-care-providers-compounders-and-consumers-potential-risks-associated-compounded
Thompson IM, Goodman PJ, Tangen CM, et al. The Influence of Finasteride on the Development of Prostate Cancer. New England Journal of Medicine. 2003. https://doi.org/10.1056/NEJMoa030660
Lee S, Lee Y, Choe S, Lee W. Adverse Sexual Effects of Treatment with Finasteride or Dutasteride for Male Androgenetic Alopecia: A Systematic Review and Meta-analysis. Acta Dermato-Venereologica. 2018. https://doi.org/10.2340/00015555-3035
Gupta AK, Charrette A. The efficacy and safety of 5α-reductase inhibitors in androgenetic alopecia: a network meta-analysis and benefit-risk assessment of finasteride and dutasteride. Journal of Dermatological Treatment. 2013. https://doi.org/10.3109/09546634.2013.813011
U.S. Food and Drug Administration. PROPECIA (finasteride) tablets, prescribing information. Revised 2022. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6f904709-65aa-44ce-b144-b4c8a0416e36
Belknap SM, Aslam I, Kiguradze T, et al. Adverse Event Reporting in Clinical Trials of Finasteride for Androgenic Alopecia: A Meta-analysis. JAMA Dermatology. 2015. https://doi.org/10.1001/jamadermatol.2015.36
Irwig MS, Kolukula S. Persistent Sexual Side Effects of Finasteride for Male Pattern Hair Loss. The Journal of Sexual Medicine. 2011. https://doi.org/10.1111/j.1743-6109.2011.02255.x
Ali AK, Heran BS, Etminan M. Persistent Sexual Dysfunction and Suicidal Ideation in Young Men Treated with Low-Dose Finasteride: A Pharmacovigilance Study. Pharmacotherapy. 2015. https://doi.org/10.1002/phar.1612
Nguyen DD, Marchese M, Cone EB, et al. Investigation of Suicidality and Psychological Adverse Events in Patients Treated With Finasteride. JAMA Dermatology. 2021. https://doi.org/10.1001/jamadermatol.2020.3385
Price VH, Roberts JL, Hordinsky M, et al. Lack of efficacy of finasteride in postmenopausal women with androgenetic alopecia. Journal of the American Academy of Dermatology. 2000. https://doi.org/10.1067/mjd.2000.107953

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