Lower numbers = closer to natural. Higher numbers = more enhanced.
Why this rating?
Dutasteride is an FDA-approved prescription medication that inhibits both Type I and Type II 5-alpha reductase, reducing serum DHT by roughly 90-94% (median, per FDA/DailyMed trial data), with some sources citing suppression up to ~98%. It is approved for BPH treatment in the USA. Like finasteride, it does not enhance muscle building or athletic performance. It is purely for hair/prostate protection. By blocking testosterone-to-DHT conversion it raises circulating testosterone modestly (FDA trial data: median +19% at 1-2 years), but that remains within the normal physiologic range and has no anabolic effect. Not WADA prohibited. Rated 1 (basically natty) because it is purely a hair/prostate side-effect management tool with no path to raising the natural muscular or athletic-performance ceiling.
Overview
A dual 5-alpha reductase inhibitor that blocks both Type I and Type II isoenzymes, reducing serum DHT by roughly 90-94% at steady state (FDA trial median; some sources cite up to ~98%), versus ~70% with finasteride. More potent than finasteride for hair loss prevention but with a very long half-life of ~5 weeks. Clinically superior to finasteride for hair count and growth in head-to-head trials. Same caveats apply: only works with testosterone-based compounds, not DHT derivatives, and worsens nandrolone-related hair loss.
Important Warnings
- •ONLY works with testosterone-based compounds
- •INEFFECTIVE with DHT derivatives (Masteron, Winstrol, Anavar, Primobolan, Proviron)
- •MAKES HAIR LOSS WORSE with Nandrolone (blocks protective conversion to weaker DHN)
- •No effect on Trenbolone (cannot be 5α-reduced)
- •Very long 5-week half-life - effects persist 4-6 months after stopping
- •Takes 5-6 months to reach steady state
- •Off-label for hair loss in USA (FDA-approved for BPH only)
- •CYP3A4 inhibitors (ketoconazole, ritonavir, verapamil) increase dutasteride levels
- •Contraindicated in pregnancy - teratogenic to male fetuses
- •Women should not handle capsules
- •Suppresses PSA by ~50% - PSA values should be doubled for comparison with untreated men when screening for prostate cancer (get a new baseline PSA at 3+ months on therapy)
- •REDUCE trial (FDA label): higher incidence of high-grade (Gleason 8-10) prostate cancer with dutasteride vs placebo (1% vs 0.5%) in men 50-75 with prior negative biopsy and elevated PSA - discuss with a physician, especially for long-term/older users
- •Hair loss gradually resumes if discontinued, as with finasteride, though effects wash out more slowly due to the longer half-life
Purpose & Use Cases
Superior Hair Loss Prevention
A 917-man phase III trial (Gubelin Harcha et al., 2014, J Am Acad Dermatol) found dutasteride 0.5mg significantly superior to finasteride 1mg for hair count (P=.003), hair width (P=.004), and investigator photographic assessment (P=.002).
Maximum DHT Suppression
Reduces serum DHT by roughly 90-94% (FDA trial median; up to ~98% in some sources) vs finasteride's ~70%. For those who need maximum DHT suppression.
Prostate Protection
Reduces prostatic DHT by 97-99%. FDA-approved for BPH.
Less Frequent Dosing Option
Due to 5-week half-life, twice or thrice weekly dosing is effective and may reduce side effect frequency.
Benefits
- Reduces serum DHT by roughly 90-94% (FDA trial median; up to ~98% in some sources), vs ~70% with finasteride
- Inhibits both Type I and Type II 5-alpha reductase
- Commonly cited as ~3x more potent than finasteride at Type II inhibition, ~100x at Type I
- Clinically superior hair count results vs finasteride in a 917-man phase III trial (P=.003)
- Can be dosed 2-3x weekly due to long half-life
- Evidence on comparative sexual side effect rates vs finasteride is mixed - some real-world data suggests lower rates, but a systematic review found no significant RCT difference
- Generic available - affordable option
Good to Know
Dual-inhibitor: stronger and much longer-acting than finasteride
Dutasteride blocks BOTH Type I and Type II 5-alpha-reductase (finasteride mainly Type II), cutting serum DHT roughly 90-94% at steady state (FDA trial median; up to ~98% per some sources) vs ~70% for finasteride, with a ~5-week half-life so it lingers for months after the last dose. More DHT suppression and better hair outcomes: but a much longer washout if side effects appear.
The same DHT rules apply
It only helps when testosterone-type androgens are being converted to DHT. USELESS on DHT-derivatives (Masteron, Winstrol, Anavar, Proviron, Primobolan) because they are already DHT; can WORSEN nandrolone/deca hair loss by blocking its reduction to the weaker 5-alpha-dihydronandrolone (DHN); and does NOTHING for trenbolone, which is not 5-alpha-reduced.
Post-5ARI syndrome plus a long half-life is a double-edged sword
As with finasteride, a minority report persistent post-discontinuation sexual/mood/cognitive symptoms (debated causation, large nocebo signal). The catch specific to dutasteride: its ~5-week half-life means that if side effects DO occur they can persist for 4-6 months. This is why many start with finasteride and only escalate to dutasteride if it is inadequate.
"DHT-prone" primer: this is the deepest suppression available
Androgenetic alopecia is genetic follicle sensitivity to DHT; a testosterone cycle raises DHT and accelerates the loss. Dutasteride gives the strongest DHT knockdown of the oral 5-AR inhibitors, so it is the option for DHT-prone users who need maximum scalp protection and found finasteride not enough.
Dosage Guidelines
| Experience Level | Dosage Range |
|---|---|
| Beginner | 0.5 – 0.5 mg/day |
| Intermediate | 0.5 – 0.5 mg/day |
| Advanced | 0.5 – 0.5 mg/day |
0.5mg is the standard dose. Due to 5-week half-life, less frequent dosing (2-3x/week) is effective and may reduce side effects. Takes 5-6 months to reach steady state. Remains detectable 4-6 months after stopping. Can be taken with or without food.
Roughly 35 days; the drug remains detectable 4-6 months after discontinuation.
Side Effects
Sexual Dysfunction
uncommonFDA/DailyMed trial data (BPH population): impotence/ED ~4.7% in the first 6 months (declining to ~1.4% by year two), decreased libido ~3.0% (declining to ~0.7%), ejaculation disorders ~1.4% (declining to ~0.5%). Evidence on whether real-world rates run lower than finasteride is mixed - a systematic review of RCTs found no significant difference between the two drugs.
May improve with time. Consider less frequent dosing. Monitor and discontinue if persistent.
Post-5ARI Syndrome
rareControversial persistent symptoms after discontinuation: low libido, ED, depression, anxiety, cognitive complaints. Similar to post-finasteride syndrome.
Remains scientifically controversial. Monitor for persistent symptoms.
Gynecomastia
rareBreast tissue growth from altered androgen/estrogen ratio. FDA trial data: breast disorders ~0.5% in the first 6 months, ~0.8% by year two.
Usually resolves with discontinuation.
Reduced Sperm Count / Semen Parameters
commonFDA trial data at 52 weeks: ~23% reduction in total sperm count, ~26% reduction in semen volume, ~18% reduction in sperm motility (sperm concentration and morphology unaffected). Recovery is incomplete in the short term - sperm count remained ~23% below baseline 24 weeks after stopping.
All parameters remained within normal reference ranges in trials, but those actively trying to conceive should discuss fertility timing/testing with a physician before starting.
Extended Washout Period
commonDue to 5-week half-life, side effects may persist 4-6 months after stopping.
Be aware of long clearance time before starting.
General Mitigation Strategies
Evidence on comparative sexual side effect rates versus finasteride is mixed - some real-world/observational reports suggest lower rates despite stronger DHT suppression, but a systematic review of head-to-head RCTs found no significant difference (and one trial reported higher dysfunction with dutasteride). The long half-life is a double-edged sword: allows less frequent dosing but means side effects persist longer if they occur. Less frequent dosing (2-3x/week) may reduce side effect frequency while maintaining efficacy.
Post Cycle Therapy (PCT)
Does not affect HPT axis directly. No PCT required. Very long half-life means effects persist months after stopping.
How It Works
Dutasteride forms stable, irreversible complexes with both Type I and Type II 5-alpha reductase enzymes. It is commonly cited as ~3x more potent than finasteride at inhibiting Type II and ~100x more potent at inhibiting Type I (in-vitro potency comparisons). This dual inhibition reduces serum DHT by roughly 90-94% at steady state (FDA trial median; some sources report up to ~98%) and prostatic DHT by up to ~99%. Does not bind to the androgen receptor directly; by sparing testosterone from conversion to DHT it modestly raises serum testosterone (FDA trial median +19%, within normal physiologic range).
Hormonal & Androgenic Profile
N/A - not an anabolic; it suppresses DHT rather than binding the androgen receptor. FDA trial data shows a median +19% increase in serum testosterone (from reduced conversion to DHT), but this stays within the normal physiologic range and confers no muscle-building benefit.
Does not aromatize and is not an estrogen tool. Deep DHT suppression slightly shifts the androgen-to-estrogen ratio (the mechanism behind rare gyno), but there is no AI/SERM relevance.
The whole point of the drug, taken to the maximum: dutasteride inhibits BOTH Type I and Type II 5-alpha-reductase, cutting serum DHT roughly 90-94% at steady state (FDA trial median; up to ~98% per some sources) vs ~70% for finasteride, with a ~5-week half-life. Like finasteride it only helps on testosterone-type androgens that convert to DHT, useless on DHT-derivatives and harmful with 19-nors (see keyFacts).
Broadly neutral on lipids/blood pressure at standard doses; not a cardiovascular driver.
Fundamentals
Reference on the practices relevant to Dutasteride: how they are done and where they go wrong. Not a recommendation to use it.
Common Stacks
- Dutasteride + Testosterone - Maximum DHT suppression for hair protection
- DO NOT use with Nandrolone/Deca - makes androgenic effects WORSE
- INEFFECTIVE with DHT derivatives: Masteron, Winstrol, Anavar, Primobolan, Proviron, Anadrol, Superdrol
- No effect on Trenbolone (structure prevents 5α-reduction entirely)
- Consider finasteride first due to shorter half-life; switch to dutasteride if inadequate
Legal Status
FDA-approved for BPH only (USA); hair-loss use is off-label. Approved specifically for androgenetic alopecia in South Korea (2009) and Japan (2015). Not a controlled substance.
Legal status varies by country and changes over time. This is a general summary, not legal advice.
WADA Status
Dutasteride is not listed on the WADA Prohibited List. It is an FDA-approved medication for prostate conditions.
References
- StatPearls - Dutasteride
- StatPearls - 5-Alpha Reductase Inhibitors
- DailyMed - Dutasteride Capsules Prescribing Information (FDA-approved label; half-life, DHT suppression, PSA, REDUCE trial, sperm parameters)
- PMC - Dutasteride vs Finasteride Systematic Review
- PMC - Finasteride vs Dutasteride clinical trials comparison (BPH; DHT/potency)
- Gubelin Harcha et al. 2014, J Am Acad Dermatol - Phase III dutasteride vs finasteride vs placebo for androgenetic alopecia (hair count/width P-values)
- Urology Times - Real-World 5-ARI Data