Finasteride
Prescription ·Exploratory record · not publication-reviewed ·Updated July 13, 2026
Finasteride is a selective inhibitor of type II 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT) in the prostate, liver, and skin. At 5 mg (Proscar), it treats benign prostatic hyperplasia (BPH), reducing prostate size and improving urinary symptoms. At 1 mg (Propecia), it treats androgenetic alopecia (male pattern baldness).
Exploratory record, not a reviewed medical publication.
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What the research says.
A quick, data-only summary. The full evidence, dosing, and sources are below.
Finasteride is a selective inhibitor of type II 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT) in the prostate, liver, and skin. NutriStack rates the supporting evidence as strong. Common adult dosing is 5 mg once daily for BPH; 1 mg once daily for androgenetic alopecia (as prescribed by your physician), though a prescriber sets the actual dose. This profile indexes 10 sources.
- Decreased libido
- Erectile dysfunction
- Decreased ejaculate volume
- Women who are or may become pregnant (teratogenic, causes hypospadias in male fetuses)1
- Handling of crushed or broken tablets by women of childbearing potential
The bottom line
Evidence rating strong. Most-documented uses: reduces prostate volume by 20-30%, improves urinary symptoms and flow rate in bph, reduces risk of acute urinary retention and need for surgical intervention. 10 sources indexed (1998–2021), with 0 interaction records on file.
How it works, mechanistically.
Core mechanism
Competitively and irreversibly inhibits type II 5-alpha reductase, reducing conversion of testosterone to DHT by approximately 70%. Since DHT is the primary androgen driving prostate growth and hair follicle miniaturization, lowering DHT levels leads to prostate shrinkage (20-30% over 6 months) and promotes hair regrowth in androgenetic alopecia.
Dosing & protocol.
Bioavailability ~65%; food does not affect absorption. Effects on prostate volume take 6-12 months to fully manifest; hair regrowth effects may take 3-6 months.
Full safety detail.
Side effects
- Decreased libido
- Erectile dysfunction
- Decreased ejaculate volume
- Gynecomastia and breast tenderness
- Post-finasteride syndrome (controversial; persistent sexual side effects after discontinuation)
- Depression and mood changes (uncommon)
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Meta-analyses & systematic reviews
5- 1Systematic review of finasteride effect in women with hirsutismPMIDSoares Júnior JM, Guimarães DZ, Simões RDS et al. · Revista da Associacao Medica Brasileira (1992) · 2021
Soares Júnior JM, Guimarães DZ, Simões RDS et al.. Systematic review of finasteride effect in women with hirsutism. Revista da Associacao Medica Brasileira (1992). 2021
- 2Association of finasteride with prostate cancer: A systematic review and meta-analysisPMIDWang L, Lei Y, Gao Y et al. · Medicine · 2020
Wang L, Lei Y, Gao Y et al.. Association of finasteride with prostate cancer: A systematic review and meta-analysis. Medicine. 2020
- 3[Finasteride: 10 years of clinical use. Systematic review of the literature]PMIDJiménez Cruz JF, Quecedo Gutiérrez L, Del Llano Señarís J · Actas urologicas espanolas · 2003
Jiménez Cruz JF, Quecedo Gutiérrez L, Del Llano Señarís J. [Finasteride: 10 years of clinical use. Systematic review of the literature]. Actas urologicas espanolas. 2003
- 4Finasteride in the treatment of clinical benign prostatic hyperplasia: a systematic review of randomised trialsPMIDEdwards JE, Moore RA · BMC urology · 2002
Edwards JE, Moore RA. Finasteride in the treatment of clinical benign prostatic hyperplasia: a systematic review of randomised trials. BMC urology. 2002
- 5Meta-analysis of randomized clinical trials of finasteridePMIDRoehrborn CG · Urology · 1998
Roehrborn CG. Meta-analysis of randomized clinical trials of finasteride. Urology. 1998
Reference material
5- 6McConnell JD et al. The long-term effect of doxazosin, finasteride, and combination therapy on the clinical progression of benign prostatic hyperplasia. N Engl J Med. 2003;349(25):2387-2398.Source linkedPMID
- 7Kaufman KD et al. Finasteride in the treatment of men with androgenetic alopecia. J Am Acad Dermatol. 1998;39(4 Pt 1):578-589.Source linkedPMID
- 8Thompson IM et al. The influence of finasteride on the development of prostate cancer. N Engl J Med. 2003;349(3):215-224.Source linkedPMID
- 9Piraccini BM, Blume-Peytavi U, Scarci F et al.. Efficacy and safety of topical finasteride spray solution for male androgenetic alopecia: a phase III, randomized, controlled clinical trial. Journal of the European Academy of Dermatology and Venereology : JEADV. 2022Source linkedPMID
- 10Gupta AK, Venkataraman M, Talukder M et al.. Finasteride for hair loss: a review. The Journal of dermatological treatment. 2022Source linkedPMID
Common questions.
Quick answers about Finasteride, drawn from the data on this page.
What is Finasteride?
Finasteride is a selective inhibitor of type II 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT) in the prostate, liver, and skin. At 5 mg (Proscar), it treats benign prostatic hyperplasia (BPH), reducing prostate size and improving urinary symptoms. At 1 mg (Propecia), it treats androgenetic alopecia (male pattern baldness).
What is Finasteride used for?
Commonly cited benefits of Finasteride include: Reduces prostate volume by 20-30%; Improves urinary symptoms and flow rate in BPH; Reduces risk of acute urinary retention and need for surgical intervention; Promotes hair regrowth and slows hair loss at 1 mg dose. NutriStack rates the overall evidence as strong.
What is a typical dose of Finasteride?
A typical adult dose of Finasteride is 5 mg once daily for BPH; 1 mg once daily for androgenetic alopecia (as prescribed by your physician). The commonly recommended form is Oral tablet. These are general ranges, not personalized advice; confirm the right dose with a clinician.
What are the side effects of Finasteride?
Reported side effects include decreased libido, erectile dysfunction, decreased ejaculate volume, gynecomastia and breast tenderness, post-finasteride syndrome (controversial; persistent sexual side effects after discontinuation), depression and mood changes (uncommon). This is educational information; check with a healthcare professional before use.
How strong is the evidence for Finasteride?
NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.
Use this with your stack
Finasteride in NutriStack.
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