Lower numbers = closer to natural. Higher numbers = more enhanced.
Why this rating?
Finasteride is an FDA-approved prescription medication for hair loss and BPH that blocks DHT conversion. It does not enhance muscle building, athletic performance, or provide any anabolic effects. Per a 12-month RCT (Borst 2013), testosterone + finasteride showed no impairment of muscle gains, meaning finasteride neither helps nor hinders muscle growth. It is purely a supportive medication for hair preservation. Not WADA prohibited. Rated 1 (basically natty): it is a cosmetic/side-effect management tool for DHT-driven hair loss, not a muscular/physique/performance enhancer, so it does not move the natural ceiling by any path.
Overview
A 5-alpha reductase inhibitor that blocks the conversion of testosterone to DHT, reducing serum DHT by 65-70%. Used during testosterone cycles to prevent DHT-related hair loss. CRITICAL: Only works with testosterone-based compounds. Does NOT work with DHT derivatives (Masteron, Winstrol, Anavar). Makes hair loss WORSE with nandrolone compounds.
Important Warnings
- •ONLY works with testosterone-based compounds
- •INEFFECTIVE with DHT derivatives (Masteron, Winstrol, Anavar, Primobolan, Proviron)
- •MAKES HAIR LOSS WORSE with Nandrolone compounds (blocks protective conversion)
- •No effect on Trenbolone or Boldenone (different pathways)
- •FDA added suicidal ideation warning in 2022
- •Contraindicated in pregnancy - teratogenic to male fetuses
- •Women should not handle crushed/broken tablets
- •Hair loss resumes within 12 months of discontinuation
- •Post-finasteride syndrome remains controversial
Purpose & Use Cases
Hair Loss Prevention During Testosterone Cycles
Blocks conversion of testosterone to DHT, preventing DHT-mediated hair follicle miniaturization. Only effective with testosterone-based compounds.
Prostate Protection
Reduces prostatic DHT by 80-90%. PCPT trial showed 25% reduction in prostate cancer risk. Prevents testosterone-induced prostate enlargement.
Preserving Testosterone Levels
By blocking DHT conversion, may increase circulating testosterone by ~15%, remaining within the normal physiologic range.
Benefits
- Reduces serum DHT by 65-70%
- FDA Propecia 5-year trials: 90% of men had no further hair loss (48% regrowth, 42% no change)
- May increase circulating testosterone by ~15% (still within physiologic range)
- Does NOT impair muscle gains from testosterone (12-month RCT confirmed)
- 25% reduction in prostate cancer risk (PCPT trial)
- Prevents testosterone-induced prostate enlargement
- Well-tolerated in most users
- Inexpensive as generic
Good to Know
The DHT / 5-AR mechanism in one line
Testosterone is converted into DHT, a much more potent scalp and prostate androgen, by the enzyme 5-alpha-reductase. Finasteride blocks that enzyme, cutting DHT by ~65-70%. Less scalp DHT means slower androgenetic (DHT-driven) hair loss and a smaller prostate.
What "DHT-prone" actually means
Androgenetic alopecia is a genetic sensitivity of your scalp follicles to DHT. If you are DHT-prone, a testosterone cycle (which raises DHT) accelerates the balding you were already genetically headed for. Finasteride blunts that acceleration by lowering DHT. It does not create hair, it slows loss.
USELESS on DHT-derivatives, WORSE on 19-nors
Finasteride only helps when the androgen is actively being converted to DHT. DHT-derivative steroids (Masteron, Winstrol, Anavar, Proviron, Primobolan) are ALREADY DHT-based. There is nothing to block, so fin does nothing. Worse, with nandrolone/deca-type 19-nors it can WORSEN hair loss: nandrolone is normally reduced by 5-AR to the much weaker 5-alpha-dihydronandrolone (DHN); block that reduction and you leave more of the stronger parent androgen active on the scalp. Trenbolone is not 5-alpha-reduced at all, so fin has no effect there.
Post-finasteride syndrome caveat
A minority of users report persistent sexual, mood and cognitive symptoms that continue after stopping (post-finasteride syndrome). Causation is genuinely debated, the nocebo signal is large (far more sides reported when users are warned), and the FDA states no proven causal link, but it added a suicidal-ideation warning in 2022. Enough of a real-world concern to weigh the drug honestly and stop if neuropsychiatric symptoms appear.
Dutasteride is the stronger, longer-acting sibling
Dutasteride blocks both 5-AR isoforms and cuts DHT ~94-98% (vs ~70% for finasteride) with a ~5-week half-life. More suppression and better hair outcomes, but a much longer washout if side effects hit, many people try finasteride first and only escalate if it is inadequate.
Dosage Guidelines
| Experience Level | Dosage Range |
|---|---|
| Beginner | 1 – 1 mg/day |
| Intermediate | 1 – 1.25 mg/day |
| Advanced | 1 – 5 mg/day |
1mg/day is the standard dose for hair loss prevention. Begin when starting testosterone cycle and continue throughout. Effects are cumulative - takes 3-4 months to see hair results. Hair loss resumes within 12 months of discontinuation. 5mg (Proscar) can be split into quarters for cost savings.
The pharmacodynamic effect outlasts plasma clearance because finasteride forms a slowly-dissociating complex with 5-alpha-reductase, per FDA labeling, enzyme-complex turnover t1/2 is ~14 days (Type I) to ~30 days (Type II), so DHT suppression persists well beyond plasma clearance.
Side Effects
Sexual Dysfunction
uncommon3.8% of finasteride users report sexual side effects (vs 2.1% placebo): decreased libido, ED, ejaculation disorders, reduced semen volume.
Generally decrease after years 2-4 of treatment. Monitor and discontinue if persistent.
Post-Finasteride Syndrome (PFS)
rareControversial condition with persistent symptoms after discontinuation (sexual dysfunction, depression, cognitive issues). True prevalence has never been firmly established; a 2017 retrospective review found persistent ED in ~0.8% of 16-42 year-olds (up to ~1.4% overall).
Remains scientifically debated. Nocebo effect is significant (~44% reported sides when warned vs ~15% when not). FDA states no proven causal link.
Depression/Anxiety
rareMechanism may involve reduced neurosteroid synthesis (allopregnanolone). FDA added suicidal ideation warning in 2022.
Monitor mood. Discontinue if neuropsychiatric symptoms develop.
Gynecomastia
rareRare breast tissue growth from altered androgen/estrogen ratio.
Usually resolves with discontinuation.
General Mitigation Strategies
Most users tolerate finasteride well. Sexual side effects occur in ~3.8% but often diminish over time. The nocebo effect is significant - studies show much higher side effect reporting when patients are warned about them. Post-finasteride syndrome remains controversial with no proven causal mechanism. Crosses blood-brain barrier which may relate to neuropsychiatric effects.
Post Cycle Therapy (PCT)
Does not affect HPT axis directly. No PCT required. Can be used long-term. May slightly increase testosterone by blocking DHT conversion.
How It Works
Finasteride is a competitive inhibitor of Type II and Type III 5-alpha reductase enzymes. These intracellular enzymes convert testosterone to dihydrotestosterone (DHT). When finasteride binds to the enzyme, it becomes inactivated and cannot convert testosterone to DHT. Reduces serum DHT by 65-70% and prostatic DHT by 80-90%. May increase circulating testosterone by ~15% (by blocking conversion to DHT), remaining within physiologic range.
Hormonal & Androgenic Profile
N/A - not an anabolic; it modulates DHT rather than binding the androgen receptor. May raise circulating testosterone by ~15% by blocking its conversion to DHT (stays within physiologic range).
Does not aromatize and is not an estrogen tool. By cutting DHT it slightly shifts the androgen-to-estrogen ratio, which is the mechanism behind the rare reports of gyno, but there is no AI/SERM relevance here.
This is the entire point of the drug: finasteride competitively inhibits Type II/III 5-alpha-reductase, cutting the testosterone-to-DHT conversion and lowering serum DHT by ~65-70% (prostatic DHT ~80-90%). It is the one 5-AR intervention that HELPS on a testosterone cycle, and is useless on DHT-derivatives and harmful with 19-nors (see keyFacts).
Broadly neutral on lipids/blood pressure at hair-loss doses; it is not a cardiovascular driver.
Fundamentals
Reference on the practices relevant to Finasteride: how they are done and where they go wrong. Not a recommendation to use it.
Common Stacks
- Finasteride + Testosterone - Primary use case, prevents DHT hair loss
- DO NOT use with Nandrolone/Deca - makes androgenic effects WORSE
- INEFFECTIVE with DHT derivatives: Masteron, Winstrol, Anavar, Primobolan, Proviron
- No effect on Trenbolone (different metabolic pathway)
- Consider RU58841 or pyrilutamide for DHT-derivative compounds
Legal Status
FDA-approved for BPH and male pattern baldness (USA). Not a controlled substance.
Legal status varies by country and changes over time. This is a general summary, not legal advice.
WADA Status
Finasteride is not listed on the WADA Prohibited List. It is an FDA-approved medication for hair loss and prostate conditions.
References
- StatPearls - 5-Alpha Reductase Inhibitors
- DailyMed - Propecia (Finasteride) FDA Label (lists depression/suicidal ideation, 65% DHT reduction, 3.8% vs 2.1% sexual AEs, ~15% testosterone increase)
- PMC - Post-Finasteride Syndrome
- PMC - Musculoskeletal Effects of Testosterone + Finasteride
- NCI - Prostate Cancer Prevention Trial