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Prescription medication — not a dietary supplement
Finasterideis a prescription (or investigational) drug, not a supplement. It is included here for reference because people research and discuss it (often used off-label) — not as a recommendation. Take it only under a qualified clinician's supervision and only as prescribed; do not source it from grey-market vendors, where identity, purity, and dosing are unverified. The evidence below reflects its clinical trials.
What the evidence says
Most Finasteride studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality meta-analyses and randomised trials published 1998–2024 with a typical study size of 3,040 participants.
Based on 8 studies · 1 meta-analysis · 5 RCTs · 28,075 total participants
Confidence
HighBy outcome
Finasteride has an evidence score of 5.5/10 — moderate evidence based on 8 indexed studies, including 2 meta-analyses. A prescription 5α-reductase type-II inhibitor that lowers DHT to treat male pattern hair loss (1 mg, Propecia) and benign prostatic hyperplasia (5 mg, Proscar). The hair and prostate benefits are well-proven in large RCTs. The honest caveats are real and prominent: sexual side effects (erectile dysfunction, decreased libido) in a minority of men, a disputed but important 'post-finasteride syndrome' with persistent symptoms, and a depression/suicidality safety signal in pharmacovigilance data. It is NOT a longevity drug. Representative study: PMID 38725143.
The commonly studied dose of Finasteride is 1 mg once daily for male pattern hair loss (Propecia); 5 mg once daily for benign prostatic hyperplasia (Proscar). A prescription drug — use under a clinician.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Dutasteride
Mostly mechanism / observationalA dual 5α-reductase (type I + II) inhibitor approved for benign prostatic hyperplasia and used off-label for male pattern hair loss. It suppresses DHT more deeply than finasteride (which blocks only type II), and head-to-head it beats finasteride for hair regrowth. It carries the same sexual and mood side-effect concerns as finasteride — with a much longer half-life, so any persistent effects clear more slowly. A prescription drug, not a supplement, and not a longevity drug.
Last reviewed June 2026 · evidence from 8 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Finasteride (Propecia / Proscar) — 5α-reductase type-II inhibitor
A prescription 5α-reductase type-II inhibitor that lowers DHT to treat male pattern hair loss (1 mg, Propecia) and benign prostatic hyperplasia (5 mg, Proscar). The hair and prostate benefits are well-proven in large RCTs. The honest caveats are real and prominent: sexual side effects (erectile dysfunction, decreased libido) in a minority of men, a disputed but important 'post-finasteride syndrome' with persistent symptoms, and a depression/suicidality safety signal in pharmacovigilance data. It is NOT a longevity drug.
Finasteride has strong, pivotal-RCT evidence for its two approved indications — durable hair retention in male pattern hair loss and reduced acute urinary retention/surgery and clinical progression in BPH — but it carries real sexual side effects, a disputed but important persistent post-finasteride syndrome, and a depression/suicidality pharmacovigilance signal, and it is not a longevity drug, so it sits mid-scale rather than higher.
Finasteride is a competitive inhibitor of 5α-reductase type II, the enzyme that converts testosterone to dihydrotestosterone (DHT). By lowering serum and scalp DHT, it treats two androgen-driven conditions.
At 1 mg/day (Propecia) it is an FDA-approved treatment for male androgenetic alopecia: the pivotal Kaufman 1998 RCT and a 5-year extension showed durable increases in scalp hair count versus progressive loss on placebo.
At 5 mg/day (Proscar) it shrinks the prostate and treats benign prostatic hyperplasia (BPH): the PLESS trial cut the risk of acute urinary retention and BPH surgery by roughly half over four years, and the MTOPS trial showed it reduced long-term clinical progression (best in combination with an alpha-blocker).
The Prostate Cancer Prevention Trial (PCPT) found finasteride reduced overall prostate-cancer prevalence by about 25% — but with an important nuance: a higher rate of high-grade (Gleason 7-10) tumors in the finasteride arm, later attributed in part to detection effects but still a reason it is not used purely for cancer prevention.
The honest counter-side is mandatory here: finasteride causes sexual adverse effects (erectile dysfunction, decreased libido, ejaculatory problems) in roughly 3-16% of men in trials; a subset report persistent sexual dysfunction that does not resolve after stopping — the contested 'post-finasteride syndrome' — and pharmacovigilance analysis of the WHO VigiBase database found a disproportionality signal for suicidality and psychological adverse events (depression, anxiety), strongest in younger men taking it for hair loss.
These harms are genuinely disputed in magnitude but important enough that they belong front and center. Finasteride is an effective, well-studied prescription drug for hair loss and BPH.
It is not a geroprotector and has no demonstrated lifespan or healthspan benefit; the score reflects strong efficacy for its indications balanced against real and contested side effects.
Competitively inhibits 5α-reductase type II, blocking conversion of testosterone to dihydrotestosterone (DHT).
Reduces serum and scalp/prostate DHT by roughly two-thirds, removing the androgenic driver of follicle miniaturization and prostate growth.
Lower local DHT slows follicle miniaturization (hair) and shrinks prostate tissue — but the same DHT reduction underlies sexual and possibly neurosteroid-mediated effects.
How Finasteride works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Tap node to isolate • Pinch to zoom • Tap edge for research
1 mg once daily for male pattern hair loss (Propecia); 5 mg once daily for benign prostatic hyperplasia (Proscar). A prescription drug — use under a clinician.
Can be taken without food
| Form | Type |
|---|---|
| 💊Oral tablet (1 mg for hair, 5 mg for BPH) | Recommended |
| 🧴Dutasteride (dual 5α-reductase type I+II inhibitor — stronger DHT suppression, similar side-effect concerns); topical finasteride (lower systemic exposure, emerging evidence) | Alternative |
Finasteride is type-II selective; dutasteride blocks both isoenzymes.
Minimum: 12 weeks
Optimal: 52 weeks
Cycling: Not required
Note: Once daily at a consistent time. Hair benefit takes months and is lost within ~12 months of stopping; continuous use is required.
Dose-response data unavailable. The current published research for Finasteride does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Durable increases in scalp hair count over 1-5 years in male pattern hair loss, versus progressive loss on placebo.
Shrinks the prostate and reduces acute urinary retention and the need for BPH surgery by roughly half over four years.
Erectile dysfunction, decreased libido, and ejaculatory problems in a minority of men; a subset report persistent symptoms after stopping (disputed post-finasteride syndrome).
Pharmacovigilance data show a disproportionality signal for depression, anxiety, and suicidality, strongest in younger men using it for hair loss.
Contraindicated — DHT suppression can feminize a male fetus; do not handle broken tablets.
Counsel explicitly on sexual side effects, the disputed persistence risk, and the mood/suicidality signal before starting.
Inform the clinician — PSA is roughly halved and must be interpreted accordingly.
Finasteride lowers PSA by ~50%; the measured value must be doubled or screening thresholds adjusted to avoid masking prostate cancer.
Co-use alters the testosterone-to-DHT ratio; the net androgenic and side-effect profile shifts and should be clinician-managed.
Tip: Reported in ~3-16% of men in trials; usually reversible on stopping, but discuss persistence risk before starting.
Tip: A disputed subset report sexual symptoms that persist after discontinuation; magnitude is contested but counsel patients, especially younger men.
Tip: Pharmacovigilance disproportionality signal (strongest in younger hair-loss users); monitor mood and stop and seek care for depressive symptoms.
Tip: Reversible in most cases; report breast changes to a clinician.
Timing is flexible for Finasteride — consistent daily use matters more than the time of day. Once daily at a consistent time, with or without food.
Finasteride should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are decreased libido / erectile dysfunction / ejaculatory problems, persistent sexual dysfunction (post-finasteride syndrome), depression / anxiety / suicidality signal. Use caution if any of these apply to you: Women who are or may become pregnant (handling crushed/broken tablets risks feminization of a male fetus); Children / adolescents; Known hypersensitivity to finasteride.
Testosterone (TRT)
Mostly mechanism / observationalThe primary male androgen and an FDA-approved prescription drug for diagnosed male hypogonadism — and a Schedule III CONTROLLED SUBSTANCE. For men with genuinely low testosterone, randomized trials show real benefits: the Testosterone Trials (TTrials) improved sexual function, mood, anemia and bone density in older hypogonadal men, and the large TRAVERSE trial found TRT non-inferior to placebo for major cardiac events. But those benefits were modest and indication-specific, NOT a longevity or anti-aging result. It is prescription-only; non-medical, supraphysiologic, and 'anti-aging' use is illegal and carries serious harms — erythrocytosis, suppressed sperm production/fertility, cardiovascular and psychiatric risk. This is a harm-reduction reference, not a recommendation, and testosterone is NOT a dietary supplement.